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HARVARD  UNIVERSITY 


GEOLOGICAL  SCIENCES 

LIBRARY 

From  the  library  of 

Jay  Backus  Woodworth 


Transferred  to 

CABOT  SCIENCE  LIBRARY 

June  2005 


WILLIAM  U.  SWAN. 


THE   ERUPTION   OF   KRAKATOA, 


AXD 


SUBSEQUENT     PHENOMENA. 


EXPLANATORY    OF    COLOURED    FRONTISPIECE. 


These  chromo-lithographs  are  reproduced  from  a  series  of  six  crayon  sketches 
made  on  the  bank  of  the  Thames,  a  little  west  of  London,  on  the  evening  of 
November  26th,  1883,  by  Mr.  W.  Ascroft,  of  Chelsea. 

They  represent  the  general  colouring  of  the  western  sky  from  shortly  after 
sunset  (3h.  57m.  p.m.)  to  the  final  dying  out  of  the  after-glow  at  about  5.15  p.m. 

The  increase  of  light  after  the  cessation  of  ordinary  twilight — that  is  to  say, 
between  Nos.  2  and  4 — is  very  marked,  and  the  gradual  change  iu  the  tone  of 
Nos.  3,  4,  5,  and  6  very  instructive. 


TwiLIGliT   AND  ArttRGLOW  tFft  f   CHLLSCA,  LONOON. 

Nov   2Q'r  1883. 


I 


V 


'^ 


r 


THE    ERUPTION    OF    KRAKATOA, 


AND 


SUBSEQUENT     PHENOMENA. 


REPORT   OF   THE   KRAKATOA   COMMITTEE 


OF  THE 


ROYAL    SOCIETY. 


VIZ.: — 


Abkrcromby,  The  Hon.  Ralph. 
Archibald,  E.  Douglas, 
BoNNEY,  Pbof.  T.  G.,  F.R.S. 
Evans,  (the  late)  Sm  F.  J.,  F.R.S. 
Geikie,  De.  a.,  F.R.S. 
JuPD,  Prof.  J.  W.,  F.R.S. 
LocKYffii,  J.  Norman,  F.R.S. 


Russell,  The  Hon.  F.  A.  Rollo. 
Scott,  R  H.,  F.R.S. 
Stokes,  Prof.  G.  G,,  Fres.  R.S. 
Strachey,  Lt.-General,  R.E.,  F.R.S. 
Symons,  G.  J.,  F.R.S.,  Chairman. 
Wharton,  Capt.  W.  J.  L.,  RN., 
F.RS. 


Edited  by  G.   J.   SYMONS,  F.R.S. 


LONDON: 
PRINTED  BY  HARRISON  AND  SONS,  ST.  MARTIN'S  LANE,  W.C, 

AND   PUBLISHED  BY 

TRt)BNER  &  Co.,  57  and  59,  LUDGATE   HILL. 

1888. 
Price  Thirty  Shillingt. 


v.. 


SPEC 


PREFATORY    AND    HISTORICAL. 


The  extremely  violent  nature  of  the  eruption  of  Krakatoa  on  August  26th-27th, 
1883,  was  known  in  England  very  shortly  after  it  occurred,  but  it  was  not  until  a 
month  later  that  the  exceptional  character  of  some  of  the  attendant  phenomena  was 
reported.  Blue  and  green  suns  were  stated  to  have  been  seen  in  various  tropical 
countries ;  then  came  records  of  peculiar  haze ;  in  November  the  extraordinary 
twilight  glows  in  the  British  Isles  commanded  general  attention,  and  their  probable 
connection  with  Krakatoa  was  pointed  out  by  various  writers. 

At  the  meeting  of  the  Royal  Society,  on  December  13th,  a  paper  by  Mr.  Scx)tt, 
and  a  note  by  General  Strachby,  gave  the  first  details  of  the  great  air- wave,  and 
indicated  its  nature  and  extent. 

On  January  10th,  1884,  papers  by  Commander  the  Hon.  F.  C.  P.  Vereker  and 
by  Mr.  Kennedy,  BLB.M.'s  Consul  at  Batavia,  describing  the  remarkable  changes  in 
the  physical  configuration  of  the  district,  were  read  before  the  Boyal  Society.  In 
the  course  of  the  discussion  upon  them,  it  was  suggested  that  it  would  be  well  to 
collect  and  coordinate  all  the  information  obtainable  respecting  the  mruption;  and 
the  President  (Professor  Huxlet)  promised  that  the  subject  should  be  brought 
before  the  Council. 

On  January  17th,  the  Coundl  passed  the  following  resolution : — ^'*  That  a 
"  committee,  to  consist  of  Sir  F.  Evans,  Prof.  Judd,  Mr.  Nobman 
"  Locrteb,  Mr.  R.  H.  Scott,  General  Strachey,  and  Mr.  G.  J. 
**  Stmons,  with  power  to  add  to  their  number,  be  appointed,  to  collect 
''  the  various  accounts  of  the  volcanic  eruption  at  Krakatoa,  and 
*'  attendant  phenomena,  in  such  form  as  shall  best  provide  for  their 
'*  preservation,  and  promote  their  usefulness/' 

The  first  meeting  of  the  Committee  was  held  on  February  5th,  all  the  members 
being  present.      It  was  resolved  that  a  letter  inviting  assistance  should  be  prepared 


[     iv     J 

for  inflertion  in  '  The  Times '  and  other  periodicak.     The  following  is  a  copy  of  that 
letter : — 


"THE  KRAKATOA  ERUPTION, 

''  Sir, — ^The  Coundl  of  the  Boyal  Sociefy  has  appointed  a  committee  for  the 
purpose  of  collecting  the  various  accounts  of  the  volcanic  eruption  at  Erakatoa,  and 
attendant  phenomena^  in  such  form  as  shall  best  provide  for  their  preservation  and 
promote  their  usefulness.  The  committee  invite  the  conmmnication  of  authenticated 
facts  respecting  the  fall  of  pumice  and  of  dust,  the  position  and  extent  of  floating 
pumice,  the  date  of  exceptional  quantities  of  pumice  reaching  various  shores, 
observations  of  unusual  disturbances  of  barometric  pressure  and  of  sea  level,  the 
presence  of  sulphurous  vapours,  the  distances  at  which  the  explosions  were  heard, 
and  exceptional  effects  of  light  and  colour  in  the  atmosphere.  The  committee  will  be 
glad  to  receive  also  copies  of  published  papers,  articles  and  letters  bearing  upon  the 
subject.  Correspondents  are  requested  to  be  very  particular  in  giving  the  date, 
exact  time  (stating  whether  Greenwich  or  local),  and  position  whence  all  recorded 
facts  were  observed.  The  greatest  practicable  precision  in  all  these  respects  is 
essential.    All  communications  are  to  be  addressed  to — 

"  Your  obedient  servant, 

"G.   J.   SYMONS, 
'^  Chairman,  Ejukatoa  Conmiittee. 
''  Royal  Society,  Burlington  House, 

'*  February  12th,  1884." 


A  secretary  also  was  appointed  who  attended  daily  at  Burlington  House 
for  about  twelve  months,  searching  many  hundred  periodicals,  and  parts  of 
*  Proceedings,'  ^  Transactions,'  &c.,  copying  out  and  classifying  the  various  state- 
ments, as  well  as  attending  to  the  correspondence  received  in  reply  to  the  published 
invitation. 

At  the  meeting  on  March  27th,  1884,  a  letter  was  read  which  had  been  received 
from  the  Royal  Meteorological  Society,  stating  that  on  January  16th  that  Society  had 
appointed  a  committee  to  investigate  the  cause  of  the  remarkable  sunrises  and 
sunsets,  and  had  already  issued  circulars  of  inquiry  over  the  greater  part  of  the  globe, 
and  suggesting  that  therefore  that  branch  of  the  inquiry  should  be  left  to  them. 
Eventually  it  was  arranged  that  all  the  data  collected  by  the  Royal  Meteorological 
Society  should  be  handed  over  to  the  Erakatoa  committee,  and  that  the  members  of 
the  committee  of  the  Royal  Meteorological  Society  should  be  made  members  of  the 
Erakatoa  committee.  The  Hon.  Ralph  Absbobombt,  Mr.  E.  Douglas  Abchibald, 
and  the  Hon.  F.  A.  Rollo  Russell,  were  so  elected. 


[  y  ] 

Coloured  drawings  of  the  twilights  were  submitted  to  the  committee  on  March 
27th,  1884,  by  Mr.  J.  S.  Dyason,  and  on  June  I9th,  1885,  by  Mr.  W:  Ascjeoft  ;  six 
of  those  submitted  by  the  latter  artist  have  been  reproduced  as  a  Frontispiece  to  this 
volume. 

At  the  meeting  on  June  18th,  1884,  Dr.  Geikie,  and  on  November  20th,  1884, 
Prof.  BoNNEY,  were  added  to  the  committee. 

At  the  end  of  November,  1884,  it  was  considered  expedient  to  commence  the 
discussion  of  the  great  mass  of  data  collected,  and  it  was  divided  into  five  portions, 
each  going  to  a  separate  sub-committee  as  follows  : — 

GEOLOGICAL. 

Including  descriptions  of  the  Eruption,  Earthquakes,  and  the  Geological  features 
relating  to  Dust  and  Pumice- 
Prof.  JuDD,  Dr.  Geikib, 
Prof.  BoNNEY,                                 Mr.  E.  H.  Scott. 

METEOEOLOGICAL.    (A.) 

Including  Air- Waves,  Sounds,  and  the  geographical  distribution  of  Dust  and 
Pumice — 

General  Strachey,  Prof  Stokes,  Mr.  R.  H.  Scott, 

METEOROLOGICAL.     (B.) 

Including  Twilight  Effects,  Coronal  Appearances,  Cloud  Haze,  Coloured  Sun, 
Moon,  &c. — 

Mr.  E.  Douglas  Archibald,  Mr.  J.  Norman  Lockyee, 

Hon.  RoLLO  Russell. 

SEISMIC  SEA    WAVES. 

Sir  F.  Evans  (and  subsequently  Captain  Welarton),  General  Strachey. 

TERRESTRIAL   MAGNETISM   AND   ELECTRICITY, 

The  Kew  Committee. 
(G.  M.  Whipple,  B.Sc,  Superintendent.) 
The  extraction  of  data  being  then  nearly  finished,  it  was  not  considered  necessary 
to  retain  the  services  of  the  secretary,  and  all  the  routine  work  for  the  subsequent 
two  years  was  conducted  by  the  Chairman. 

On  the  death  of  Sir  F.  Evans,  the  President  and  Council  of  the  Royal  Society 
nominated  Captain  Wharton  as  a  member  of  the  committee,  and  he  has  completed 
the  investigation  of  the  Seismic  Sea  Waves. 


[     vi     ] 

Thus  it  will  be  seen  that  28  months  elapsed  between  the  distribution  of  the  data 
to  the  various  sub-committees  and  the  completion  of  the  report  and  its  transmission 
to  the  Council.  But  it  is  to  be  remarked  that  the  optical  phenomena  did  not  entirely 
fade  from  view  until  the  early  part  of  1886,  and  that  besides  the  great  mass  of 
material  originally  distributed,  a  constant  flow  of  additional  literature,  including  the 
very  valuable  report  by  Mr.  Yeebeek,  has  been  received  and  transmitted  to  the 
writers  of  the  various  Parts. 

As  regards  the  mass  of  material,  it  may  be  mentioned  that  it  has  included — 

Barograms  firom  50  observatories, 
Magnetograms  from  1 1       „ 
Tidal  Becords     ,,     50  stations. 

Between  300  and  400  letters  have  been  received,  most  of  them  enclosing  bulky 
reports.  Many,  being  written  in  foreign  languages,  have  required  translation,  and 
all  have  required  the  conversion  of  their  local  times  into  6.M.T.,  and  of  course  the 
answering  and  forwarding  of  these  letters  has  involved  much  clerical  labour. 

The  printed  literature  on  the  subject  has  been  very  extensive,  as  is  shown  by  the 
appended  list  of  books  and  papers  consulted,  and  the  work  altogether  has  been  very 
heavy,  for  it  has  not  only  extended  back  to  the  year  1500,  but  it  has  ramified 
through  many  branches  of  physics,  and  has  involved  extensive  correspondence  with 
all  parts  of  the  globe. 

In  the  spring  of  1887  the  MS.  was  completed  and  submitted  to  the  Council  of 
the  Boyal  Society,  together  with  estimates  of  the  cost  of  publication.  The  Council, 
while  of  course  expressing  no  opinion  upon  the  work,  authorised  the  committee  to 
proceed  with  the  printing. 

I  hope  that  I  may  here  be  permitted  on  behalf  of  the  committee  to  acknowledge 
the  constant  and  great  help  which  we  have  received  throughout  from  the  President, 
Ofl&cers,  and  Council. 

The  volume  itself  wiU  show  the  amount  of  heavy  work  done  by  the  various 
authors,  and  who  is  responsible  for  the  several  arguments  and  opinions.  I  wish, 
however,  to  point  to  one  unusual  feature,  viz.,  the  hundreds  of  references  which 
are  given.  The  committee's  first  duty  (and  desire)  was  to  collect  facta  This  duty 
we  have  all  tried  to  discharge,  and  we  have  not  only  collected  the  facts,  but  have 
done  our  utmost  to  enable  everyone  to  verify  theiu. 

G.  J.  Symons. 

Burlington  House,  W.,  December^  1887. 


[     vii     ] 


List    of    some    op    the    Principal     Books    and   "Papers   published   i^especting 
THE  Phenomena  reported  upon  in  this  Volume. 


Aitken,  John.  The  Remarkable  Sunsets.  'Proc.  Royal 
Society  of  Edinbui^h,'  vol.  zii. 

Second  Note  on  the  Remarkable  Sunsets.  *  Proc. 

Royal  Society  of  Edinburgh,'  voL  xii 

AxLffot,  A.    .  Sur    les    cr6pu8cules    color^       'Coraptes 

Rendus/  vol  zcviii.,  p.  164. 
JkTWLgo,  P.     The  Comet :  Scientific  Notices  of  Comets  in 

general,  translated  by  Col.  Gold.     1833. 
Aaainaim,  Dr.  B.    Die  Dammerungs-Erscheinungen  und 

der  braune  Ring  um  die  Sonne  im  dies-jahrigen  Winter 

nnd  Friihjahr,  nach  Beobachtungen  in  Magdeburg  und 

im  Harze.     *  Meteor.  Zeita,'  vol.  i.,  pp.  196-198.     1884. 
B  aixd,  Vajor,  B.B.    On  the  Tidal  Disturbances  caused  by 

the  Volcanic  Eruptions  at  Java.     *  Proc.  Royal  Soc,' 

vol.  xxzvi.,  pp.  248-253. 

Report  on  the  Volcanic  Eruptions  at  Java  in 

August,  1883.     Sm.  fol.,  Dehra  Dun.     1884. 

Bealixy,  J.  T.  The  Java  Eruption  and  Earthquake  Waves. 
•Nature,'  vol.  xxix.,  pp.  30-32.     188a 

Beaold,  ProflBMor  von.  Ueber  die  ausserordentlichen  Dam- 
merungs-Erscheinungen.   *  Zeits.  fUr  Met.'  (1884),  p.  72. 

Biffffs,  A.  B.  Mercury  (Hobart  Town).  March  19,  April 
3,  July  12  and  22,  1884. 

Bishop,  8.  E.  The  Equatorial  Smoke-Stream  from 
Krakatoa.     '  Hawaiian  Monthly,'  May,  1884. 

Origin  of  the   Red  Glows.      'American  Met. 

JourV  July  ftnd  August,  1886.  (Printed  also  as  one 
of  the  Prize  Essays  in  '  History  and  Work  of  the 
Warner  Observatory,'  voL  i.     1887.) 

Bouquet  da  la  Grye.  Sur  la  propagation  des  lames  pro- 
duites  par  T^ruption  des  volcans  de  Java.  (Ao&t,  1883.) 
*  Comptes  Rendus,'  voL  xcvii,  pp.  1228-1230. 

BoixUUa  O.  O.  Water  Waves  from  Krakatoa.  '  Science, 
voL  iii.,  pp.  776,  777.     1884. 

Br6oii  «t  Korthals.  Sur  r6tat  actuel  du  Elrakatau. 
^  Comptes  Rendus,'  vol.  xciz.,  pp.  395-397.     1884. 

Bni«mans,  8.  J.  Natuurkundige  verhandeling  over  een 
Zwavelagtigen  Nevel  den  24  Juni,  1783,  in  de  Pro- 
vintie  van  Stad  en  Lande  en  naburige  landen  waar- 
geuoiuen.    8vo.,  Groningen.    [1783.] 


Burton,  Captain,  B.  F.     The  Volcanic  Eruptions  of  Ice- 
land in  1874  and  1875,  with  two  maps  of  Icelaud.   '  Proc. 

Royal  Society  of  Edinburgh,'  Session  1875-76,  vol.  ix. 
COark,  J.  Edmund.       The  Recent  Sky-Glows.      Warner 

Prize    Essay,  'Hist  and  Work  of  the  Warner  Obs.,' 

voL  I     1887. 
Oomu,  A.    Observations  relatives  a  la  coiu-onne  visible 

actuellement    autour  du  SoleiL       'Comptes    Rendus,' 

vol.  xciz.,  pp.  488-493.     1884. 
Cotteau  et  Korthals.     Mission  Fran^aise   aii  Krakatau. 

*Compte  Rendu,  Soc.  G6og.,'  No.  15,  pp.  452-455.  1884. 
Dall,  W.  H.     A  new  Volcano  Island  in  Alaska.    '  Science, 

vol.  iii.,  pp.  89-9a 
Daubree.    Ph^nomdnes  volcaniques  du  d6troi t  de  la  Sond  e, 

examen  min6ralogique  des  cendres.     '  Comptes  Rendus,' 

vol.  xcvii,  pp.  1100-1105(1883);  voL  xcviiL,  p.   1303 

(1884). 
Davidson,  Geo.    Notes  on  the  Volcanic  Eruption  of  Mt.  St 

Augustin.     '  Science,'  vol.  iiL,  pp.  186-189,  and  282-286. 
Davy,  lCari»-    Sur  les  oscillations  barom^triques. '  Com  ptes 

Rendus,'  voL  xcviii.,  pp.  246-248.     1884. 
De  lok  Bive.    Note  sur  la  seconde  coloration  du  Mont 

Blanc.      '  Bibliothdque    Universelle,'    Nouvelle    S^rie, 

voL  xxiii.,  p.  383  ;  vol.  xxiv.,  p.  200.     1839-40. 
Dellale,  Dr.     Les  secousses  de  tremblement  de  terre  a  la 

Reunion  et  k  Maurice  comme  consequence  de  I'^ruption 

volcanique  du  d^troit  de  la  Sonde.     'Bull.  Soc.  G6og. 

pp.  524-526.     1883. 
Deaoroiz,  Leon.   L'oecillation  atmosph^rique  produite  par 

r^ruption  de  Krakatoa.     '  L' Astronomic,'  3rd  Ann6e, 

pp.  183,  184.     1886. 
Diller,  J.  S.    Report  on  Atmospheric  Sand-dust  from 

Unalaska.     '  Nature,'  voL  xxx.  (1884),  pp.  91-93. 
Divers,  Trot,  B.     The  Remarkable  Sunsets.      'Nature, 

vol  xxix.  (1884),  pp.  283,  284. 
Doom,  K.  O.  van.  (Captain  of  ffydrograaf).    The  Eruj  - 

tion  of  Krakatoa.     'Nature,'  voL  xxix.  (1884),  pp.  268, 

269. 
Dufour,  Ch.     Les  lueurs  cr^pusculaires  de  I'hiver  1883- 

1884.     '  Bibliothdque  Univer.,'  15th  Fev.,  1885. 


[     viii     J 


Bufour,  Ch«     Sur  les  luears  cr^pusculaires  et  aurorales  de 

rhiver  de  1883-4.     *  Ck>mpte8  Bendus,'  voL  xcviii.,   pp. 

617-620.     1884. 
Faye.     Sur  les  troubles  physiques  de  ces  demiers  temps. 

*Comptes  Rendus,'  vol.  xcviii.,  pp.  179, 180. 
Flgnier,  Ii.       Les    lueurs     cr^pusculaireB    de    1883-84. 

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1885. 


CONTENTS. 


PAas 
Explanation  op  Coloubbd  Fbontispiece. 
Prefatory  and  Historical      ...  ...  ...  ...  ...  ...  ...  ...       Hi. 

List  op  some  Books  and  Papers  published  rbspbcting  the  Phenomena  reported  upon  ...       vii. 


PART  I. 

ON  THE  VOLCANIC  PHENOMENA  OF  THE  ERUPTION,  AND  ON  THE  NATURE 
AND  DISTRIBUTION  OP  THE  EJECTED  MATERIALS.  By  Professor  J.  W. 
JuDD,  1*.J3.S.,  President  of  the  Geological  Society    ...  ..  ...  ...  ...     1-56 

Introduction  ...  ...  ...  ...  ...  ...  ...  ...  ...  1 

Sketch  of  the  History  of  the  Volcano  op  Krakatoa    ...  ...  ...  ...  ...  3 

Eruption  of  1680  (10) ;  Eruption  of  May,  1883  (11)  ;  Eruption  of  August  26tli,  27tli, 
1883  (14)  ;  Smoke  column,  estimated  as  17  miles  high  (19)  ;  Rain  of  pumice' (19)  ;  Sul- 
phurous smell  (19) ;  Phosphorescent  mud  rain  (21)  ;  Two- thirds  of  the  island  disap- 
peared (22);  Vessels  stranded  by  seismic  waves,  and  36,380  persons  washed  away  or 
otherwise  killed  (26)  ;  Darkness  extended  150  miles  from  volcano  (27)  ;  Great  fall  of  dust 
and  mud  (27)  ;  Eruption  compared  with  those  of  other  volcanos  in  1772,  1783,  and 
1815  (29). 

The  Materuls  ejected  from  Krakatoa  ...  ...  ...  ...  ...        29 

Geological  structure  of  EIrakatoa  (29). 

TheLavas     ...  ...  ...  ...  ...  ...  ...  .  ..         30 

Analysis  of  pumice  (32)  ;  Other  analyses  (33). 

ThePwnice,,,  ...  -  ...  ••  ...  ...  ..  ...  ...  ...         36 

Mr.  Waller's  analysis  (38). 

The  Volcanic  Dust       ...  ...  ...  ...  ...  ...  ...  ...  ...         38 

Analyses  of  dust  which  fell  at  Krakatoa,  and  100  and  900  miles  from  it  (40). 

General  Oonclwions     ...  ...  ...  ...  ...  ...  ...         42. 

Mr.  R.  H.  Scott,  F.E.S.,  on  the  Pumice  .  .  ...  ...  ...  ...  ...        47 

A  Tabular  Statement  of  the  Dates  on  which,  and  the  Localities  where,  Pumice  or  Volcanjo 

Dust  was  seen  in  the  Indian  Ocean  in  1883-4.    By  Charles  Meldrum,  LL.D.,  F.B,8,        48 
Explanation  of  Plates  II.,  IIL,  and  IV.  ...  ...  ..  ...  ...         follow    56 


M 


[     ^ii     ] 


PART  II. 

PAGE 

ON  THE  AIR  WAVES  AND  SOUNDS  CAUSED  BY  THE  ERUPTION  OF 
KRAKATOA  IN  AUGUST,  1883.  Prepared  in  the  Meteorological  Office,  and  pre- 
sented by  Lieutenant- General  R.  Strachky,  F.li.S.,  Chairman  of  the  MeteoVological 
Council         ...  ...  ...  ...  ...  ...  ...  ...  ...       57-88 

Section  I. — Air  Wavks        ...  ...  ...  ...  ...  ...  ...  ...  57 

Station.s  from  which  barometrical  or  other  observations  have  been  received,  with  a 
description  of  the  recording  instruments  and  dates  (58)  ;  Geogi'aphical  position  of 
Krakatoa,  and  of  the  principal  stations  from  which  data  have  been  supplied  (62)  ; 
Times  of  passage  of  air-waves  over  each  station  (65)  ;  Probable  moment  of  great 
explosion  (69)  ;  Batavia  gasometer  indicator  (69)  ;  Velocities  of  air  waves  (70). 

Skction  II. — Sounds  ...  ...  ...  ...  ...  ...  ...  ...  79 

Detonations  heard  over  nearly  one-thirteenth  of  the  surface  of  the  globe  (79)  ; 
Sounds  heard  at  Rodriguez,  more  than  2,500  miles  from  Krakatoa  (79)  ;  List  of  places 
at  which  sounds  were  heard  (80). 


PART  III. 

ON  THE  SEISMIC  SEA  WAVES  CAUSED  BY  THE  ERUPTION  OF  KRAKATOA, 
AUGUST  26th  and  27th,  1888.  Bj  Captain  W.  J.  L.  Wharton,  E.N,,  KB.S.,  in 
Completion  of  the  Unfinished  Notes  of  Captain  Sir  F.  J.  Evans,  B,N,^  K.CB.y  FM.S.    89-151 

Account  of  the  phenomena  relating  to  sea  disturbance  in  the  immediate  vicinity  of 
Krakatoa  (90)  ;  Chinese"  camp  at  Merak  swept  away,  village  of  Sirik  submerged,  Anjer 
swept  away,  Telok  Betong  submerged,  Tyringen  destroyed  (90)  ;  1^  cubic  miles  of 
Krakatoa  blown  away,  the  Peak  of  Krakatoa  shorn  in  two  (93 )  ;  Former  surveys 
untrustworthy  (91)  ;  Verlaten  Island  increased  threefold.  Two  new  islands  of  mud 
and  pumice  (92)  ;  A  wave  135  feet  high.  A  man-of-war  carried  18  miles  inland  up  the 
valley  and  left  30  feet  above  the  sea-level.  The  great  wave,  how  formed.  The  island 
shrouded  in  smoke  and  fire  (93)  ;  Batavian  tide-gauge  (94) ;  The  record  of  the  seismic 
sea  waves  (95)  ;  The  cause  of  the  great  waves  (97)  ;  The  missing  mass  of  Krakatoa 
estimated  at  200,000,000  ^cubic  feet  (98)  ;  The  experimental  explosions  at  Spithead  (99)  ; 
A  wall  of  water  150  feet  high  (99)  ;  Wave  movements  in  connection  with  the  Krakatoa 
eruption  (100)  ;  Table  showing  height  of  wave  (106)  ;  Tidal  diagrams  (107)  ;  The  Sur- 
veyor General's  Report  on  the  tidal  waves  at  Ceylon  (116) ;  Sea  ebbed  and  flowed 
sixteen  times  in  three  hours  (319)  ;  Bones'  Island  partly  washed  away  (122)  ;  The  time 
between  the  crests  of  the  long  waves  (126) ;  Main  conclusions  (148)  ;  Speed  of  free 
waves,  by  Sir  George  Airy  (149)  ;  List  of  tidal  diagrams  (150);  Tabular  result  of 
discussion  of  seismic  sea- waves  from  Krakatoa  (150). 


[   Jf'"  ] 


PART  IV. 

PAOB 

ON  THE  UNUSUAL  OPTICAL  PHENOMENA  OF  THE  ATMOSPHERE,  188^-6, 
mCLUDINO  TWILIGHT  EFFECTS,  CORONAL  APPEARANCES,  SKY  HAZE, 
COLOURED  SUNS,  MOONS,  Ac.  By  the  Hon.  F.  A.  Rollo  Russell  and  Mr.  E. 
Douglas  Archibald    ...  ...  ...  ...  ...  ...  ...  ...  161-463 

Section  I.  (a). — Descriptions  op  the  Unusual  Twilight  Glows  in  various  parts  of  the  World.  152 

Selections  from  correspondence  (153)  ;  DijSerences  between  tke  nnnsnal  twilight 
glows  and  the  ordinary  sanset  effects  (172). 

Section  I.  (b). — Proximate  Physical  Cause  of  the  Unusual  Twilight  Glows       ...  ...  178 

The  eruption  of  Cotopaxi  (183)  ;  Fragments  of  babbles  of  glass  so  small  that  from 
4000  to  25,000  were  required  to  make  a  grain  in  weight  (183)  ;  1,000,000,000 
to  10,000,000,000  cavities  in  a  cubic  inch  (183)  ;  Arago  on  the  prolonged  twilights  of 
1831  (191) ;  Summary  of  evidence  respecting  the  particles  of  dust  (195) ;  Professor 
Kiessling  on  the  after-glows  (196)  ;  Professor  Bicco  on  the  after-glows  (198). 

Section  I.  (c). — The  Blue,  Green,  and  other  Coloured  Appearances  of  the  Sun  and  Moon  199 

list  of  places  at  which  the  sun  was  observed  to  be  blue,  green,  or  silvery  (204) ; 
Professor  Michie  Smith  on  the  green  sun  in  the  tropics  (210)  ;  Professor  Piazsi  Smith 
and  others  on  coloured  suns  as  seen  through  various  media  (213)  ;  Summary  (217). 

Section  I.  (d). — ^The  Skt-haze  and  some  or  its  Effects  ...  ...  ...  ...  219 

Peculiar  features  of  the  haze  (223)  ;  Colour  of  the  moon  during  the  total  eclipse  on 
October  4th,  1884  (225)  ;  Secular  duration  of  the  haze  (227)  ;  Summary  (229). 

Section  I.  (e). — ^The  large   Corona    round   the    Sun  and  Moon    in   1883-4-5,  generally 

KNOWN  AS  "Bishop's  Ring"     ...  ...  ...  ...  ...  ...  ...  232 

Table  giving  date,  observer's  name,  locality,  and  remarks  (234) ;  Table  giving  the 
angular  diameter  of  corona  round  the  sun  (235)  ;  Table  giving  the  angular  diameter  of  - 
corona  round  the  moon  (236)  ;  Diurnal  and  secular  duration  of  the  large  corona  (238)  ; 
Table  giving  the  period  of  its  continuance,  observer,  or  authority,  and  locality  (239) ; 
Dates  on  which  the  corona  has  been  seen  since  the  summer  of  1884  (240) ;  Mean 
intensity  of  the  Corona  (241) ;  Peculiar  features  of  the  corona  (242)  ;  Disappearance 
of  Bishop's  Ring  id  Colorado  (246) ;  Connection  between  Bishop's  Ring  and  the  unusual 
twilights  (247) ;  Professor  Ricc5's  opposition  to  the  views  of  Drs.  Riggenbach  and 
Eliessling  (249)  ;  General  opinions  regarding  the  corona  (251)  ;  Summary  (255). 

Appendices  to  Corona  Section  1.  (e). — Discussion  and  account  of  experiments  in  connection 
with  diffraction  coronas  and  Bishop's  Ring,  by  Professor  Kiessling  (258)  ;  Polari*- 
BGopic  observations,  by  M.  Comu  (261). 

Section  II. — General  List  of  Dates  of  First  Appearance  of  all  the  Optical  Phenomena  263 

Seotton  III.  (a). — General  Geographical  Distribution  of  all  the  Optical  Phenomena  in 

Space  and  Time  ;  including  also  VELOCiTr  of  Translation  of  Smokb  Stream  ...  312  - 

Geographical  distribution  of  peculiar  sky  phenomena  (312)  ;  Summary  (323). 


[     xiv     ] 

TJLQM 

Section  III.  (b). — Connection  between  the  Propagation  of  the  Sky-uaze  with   its  accom- 
panying OpriCAL  Phenomena,  and  the  General  Circulation  of  the  Atmosphere      ...  326 

Table  of  districts  east  of  Krakatoa,  with  distances,  and  daration  of  darkness,  ashes, 
&c,  (327)  ;  Ditto  west  of  Elrakatoa  (328)  ;  Tables  of  mean  velocity  of  ash  stream  in 
miles  per  hoar  (330  and  333) ;  Rev.  S.  £.  Bishop  on  the  equatorial  Fmoke  stream  (333)  ; 
Materials  from  Krakatoa  shot  obliquely  to  a  distance  of  from  30  to  70  miles  (334),  and 
vertically  to  a  height  of  31  miles  (334). 

Section  III.  (c). — Spread  op  the  Phenomena    roond  the    World,  with   Maps   Illustrative 

thereof         ...  ...  ...  ...  ...  ...  ...  ...  ...  334 

The  spread  of  the  phenomena  round  the  world  (334)  ;  Statistical  details  connected 
therewith  (335)  ;  Speed  of  progp:%ssion  of  blue  sun  phenomena ;  of  the  haze,  and  of  the 
red  fore-glows  and  after-glows  (337). 

Section  IV. — Diurnal  a^d    Secular  Variation   in  the   Duration  and   Brilltancv  of  the 

Twilight  Glows,  and  the  Height  above  the  Earth  of  the  Stratum  which  caused  them  340 

Prof.  Story-Maskelyne  on  the  twilight  glows  (340)  ;  List  of  observers  of  two  glows 
at  sunrise  or  sunset  (344)  ;  Duration  of  the  twilight  glows  (345)  ;  Height  of  stratum 
which  produced  the  glow  effects,  estimated  by  different  observers  (348)  ;  FormulsB  and 
calculations  respecting  the  altitude  (350)  ;  Summary  (380). 

Section  V. — Previous  Analogous  Glow  Phenomena,  and  corresponding  Eruptions  ...  384 

List  of  principal  ascertained  volcanic  eruptions  from  1500  to  1886  (384)  ;  List  of 
remarkable  atmospheric  phenomena,  such  as  blue  suns,  dry  fogs,  and  red  twilights  (384)  ; 
Notes  respecting  detailed  accounts  of  twilight  phenomena  m  some  particulai's  similar 
to  those  of  1883  (404). 

Section  VI. — Individual  Opinions  expressed  and  Hypotheses  suggested  to  account  for  the 

ABNORMAL   OPTICAL   PHENOMENA...  ...  ...  ...  ...  ...  ...  4G6 

List  of  authorities  quoted  in  this  section  (425). 

Section  VII. — General  Analysis  of  the  Connection  between  the  unusual  Meteorological 

Phenomena  of  1883-6,  and  the  Eruptions  of  Krakatoa  in  May  and  August,  1883  ...  426 

Discussion  of  various  objections  (426)  ;  Diagram  of  atmospheric  circulation  (432)  ; 
Summary  of  the  evidence  in  favour  of  the  connection  of  all  the  optical  phenomena  with 
the  eruptions  of  Krakatoa  (45G). 


PART    V. 

REPORT  ON  THE  MAGNETICAL  AND  ELECTRICAL  PHENOMENA  ACCOM- 
PANYING THE  KRAKATOA  EXPLOSION.  Prepared  at  the  request  of  the 
Kew  Committee,  bj  G.  M.  Whipple,  B.Sc.y  Superintendent  of    the  Kew  Observatory, 


Richmond,  Surrey 
Index  of  Places  mentioned  in  the  Report 
Index  of  Persons  mentioned  in  the  Report 
Index  of  Ships  mentioned  in  the  Report 


465 
476 
486 
491 


[     '^v     ] 


ILLUSTRATIONS. 


Pi.OB 

J  Pbontispiece. — Golonred  Ckromo-Lithographs  of    Sunset-Glows  as  seen  at  Chelsea,  NoTember 

26th,  1883.  Precede  Title. 

•  Plate  L — View  of  EZrakatoa  during  the  May  Eruption      ...  ...  ...  ...  faces       1 

Fig.  1.— Sketch-Map  of  the  Sunda  Strait,  showing  the  Lines  of  Volcanic  Fissure  which  appear 

to  traverse  the  District          ...              ...              ...              ...              ...              ...              ...  4 

Fig.  2. — Sketch  of  the  Island  of  Sebesi,  as  seen  from  the  north-east...              ...              ...              ...  5 

Fig.  3. — Map  of  the  Islands  of  the  Krakatoa  Group  (from  the  Admiralty  Chart)          ...             ...  6 

Fig.  4. — Outline  Section,  viewed  from  S.W.,  showing  the  position  of  the  Volcanic  Cones  upon  the 

Island  of  Krakatoa  previous  to  the  Eruption      ...  ...  ...  ...  ...  6 

Fig.  5. — Probable  Outlines  of  the  Volcano  of  Krakatoa,  at  the  period  of  its  maximum  dimensions  7 

Fig.  6. — Probable  Outlines  of  the  great  Crater  Ring  ("basal  wreck")  of   Krakatoa  Volcano, 

after  the  paroxysmal  outbursts  ...  ...  ...  ...  ...  ...    .       8 

Fig.  7. — Probable  Outlines  of  the  Krakatoa  Volcano  after  the  great  Crater  had  been  filled  up  by 

the  growth  of  numerous  small  Cones  within  it  ...  ...  ...  ...  ...  8 

Fig.  8. — Form  of  Krakatoa  in  Historical  Times  after  the  Formation  of  the  great  Lateral  Cone  of 

Rakata,  and  the  growth  of  other  Cones  within  the  great  Crater    ...  ...  ...  9 

Fig.  9. — Chart  of  Sunda  Strait  to  illustrate  the  Positions  of  the  Towns  and  the  Tracks  of  the 
Vessels,  where  the  most  important  observations,  bearing  on  the  great  final  outburst 
at  Kraktaoa,  were  made 

Fig.  10. — Outline  of  the  Crater  of  Krakatoa  as  it  is  at  the  present  time,  and  showing,  by  dotted 
lines,  the  portions  blown  away  in  the  paroxysmal  outburst  of  August,  1883... 

Fig.  11. — ^Map  of  Krakatoa  and  the  surrounding  Islands,  from  the  Chart  prepared  immediately 
after  the  Eruption  ... 


PIiATB 

'  II. — Two  views  of  Krakatoa  after  August ... 

'III. — Sections  of  Rocks  ... 

^  rV. — Sections  of  Pumice 
•  V. — Chart  showing  Sites  of  Pumice  in  the  Indian  Ocean,  August-December,  1883 
VI. — Chart  showing  Sites  of  Pumice  in  the  Indian  Ocean,  January-November,  1884 
^VII. — Enlarged  copies  of  selected  Barograms 
•  VIII. — Barometer  Curves  from  forty  stations  ... 

^  IX. — Record  of  Batavia  Gasometer 
^  X. — Passage  of  Air- Waves  I.  and  II. 

^  XI. — Passage  of  Air- Waves  III.  and  IV.     ... 


follow 


17 
23 
24 

56 
56 
56 
56 
56 
88 
88 
88 
88 


[     xvi     ] 


PLATB 

>  XII. — Passage  of  Air- Waves  V.  and  VI. 
XI II.— Passage  of  Air- Wave  VII. 

XIY.  and  XY. — Diagrams  Ulastrating  Variations  in  velocity  of  air- wave 
XVI. — ^Area  over  which  the  sounds  were  heard 
Fig.  12.— Map  of  Ceylon 

PLATR 

XVII.  to  XXXI. — Beprodnction  of  Tidal  Diagrams  (for  list  see  p.  150) 
XXXII. — Snnda  Strait  66/bre  the  Eruption... 
XXXIII.— Sunda  Strait  a/fer  the  Eruption    ... 
XXXIV.— Java  Sea 
XXXV. — Mercator's  Chart  of  the  World,  showing  Path  of  Seismic  Sea- Waves  .. 
Fig,  13. — Diagram  of  Sunset  Colours     ... 
Fig.  14. — Diagram  of  Twilight  Glows    ... 

FLATS 

XXXVI. — Distribution  of  Optical  Phenomena  over  the  Globe  ... 
XXXVII. — Distribution  of  Optical  Phenomena  at  various  dates 
XXXVIII. — Measurement  of  the  height  of  Sun-glow  Stratum     ... 
Fig.  15. — ^Diagram  of  Height  of  Glow  Stratum    ... 

FLATS 

XXXIX. — Curves  illustirative  of  Altitude  of  Glow  Stratum 
Fig.  16. — Diagram  of  Atmospheric  Circulation     ... 

PLATS 

XL.  —Copies  of  traces  produced  by  Magnetographs  at  the  time  of  the  Ejakatoa 

XDI. — Eral{  atoa  Magnetic  Disturbance.     Declination 
XLII. —         „  „  ,,  Horizontal  Force .. . 

XLIII. —         „  „  „  Vertical  Force    ... 


PACK 

follow     88 

88 


... 

88 

... 

117 

follow 

150 

»> 

152 

»» 

152 

)) 

162 

»1 

152 

... 

160 

175 

face 

334 

i» 

334 

>» 

352 

... 

354 

face 

SM 

... 

432 

explosion 
follow  474 

91 

474 

?» 

474 

91 

474 

ffr'aJcatoou.  Rep.  Roy.  Soc.  Com . 


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Parksr  &  Coward.  lUh. 


West  JSrvwrnau  It  Co  ianf 


View  of  Ki-akatoa.     d';j.rirj.^     the    Eaur-lier    Stage   of  Lhe   .triiption. 
•ProTTu  ou  PhxftoqroLpJv  uxke^n.,  otu  Svun,4Lcu/  thue  21^  of  May,  1883. 


PART    I. 


ON  THE  VOLCANIC  PHENOMENA  OF  THE  ERUPTION,  AND  ON  THE 
NATURE  AND  DISTRIBUTION  OF  THE  EJECTED  MATERIALS. 

By  Professor  J.  W.  Judd,  F.RS.,  President  of  the  Geological  Society. 


Introductory. 

During  the  closing  days  of  the  month  of  August,  1883,  the  telegraph-cahle  from 
Batavia  carried  to  Singapore,  and  thence  to  every  part  of  the  civilised  world,  the 
news  of  a  terrible  subterranean  convulsion — one  which  in  its  destructive  results  to 
life  and  property,  and  in  the  startling  character  of  the  world-wide  effects  to  which  it 
gave  rise,  is  perhaps  without  a  parallel  in  historic  times. 

As  IS  usual  in  such  cases,  the  first  reports  of  this  tremendous  outburst  of  the 
volcanic  forces  appear  to  have  been  quite  misleading  and  altogether  unworthy  of 
credence.  Nor  is  this  to  be  wondered  at.  The  towns  and  villages  along  the  shores 
of  the  Sunda  Strait  were,  during  the  crisis  of  the  eruption,  enveloped  in  a  terrible 
darkness,  which  lasted  for  many  hours,  and,  while  thus  obscured,  were  overwhelmed 
by  a  succession  of  great  sea- waves  ;  those  who  succeeded  in  saving  their  lives  amid 
these  appalling  incidents  were,  it  need  scarcely  be  added,  not  in  a  position  to  make 
trustworthy  observations  upon  the  wonderful  succession  of  phenomena  occurring 
around  them. 

For  some  time  after  the  eruption,  the  Sunda  Strait  Was  almost  impassable  ;  light- 
houses had  been  swept  away,  all  the  old  familiar  landmarks  on  the  shores  were 
obscured  by  a  vast  deposit  of  volcanic  dust ;  the  sea  itself  was  encumbered  with 
enormous  masses  of  floating  pumice,  in  many  places  of  such  thickness  that  no  vessel 
could  force  its  way  through  them ;  and  for  months  after  the  eruption  one  of  the 

B 


2  PBOF.  JUDD  OX  THE  VOLCANIC  PHENOMENA. 

principal  channels  was  greatly  obstructed  by  two  new  islands  which  had  arisen  in  its 
midst. 

The  first  accounts  brought  to  Europe  stated  that  Thwart-way  Island,  situated  at 
the  ed|tern  entrance  of  the  Strait,  had  been  split  into  five  portions ;  that  the  Cape 
of  Ar^r  had  been  sundered  by  a  great  fissure ;  that  a  number  of  small  islands 
had  subsided ;  and  that  no  fewer  than  sixteen  volcanoes  had  burst  into  eruption 
within  the  Strait.  Subsequently,  however,  it  was  found  that  those  who  had  first 
made  their  way  into  the  Strait  after  the  great  convulsion,  had  been  altogether  misled 
by  the  hasty  and  imperfect  glimpses  which  they  had  obtained  of  the  desolated  district, 
and  that  the  real  centre  of  the  volcanic  disturbance  was  at  Krakatoa,  the  actual 
eruptions  being  confined  to  that  island  and  the  district  immediately  surrounding  it. 

The  first  efibrts  of  the  Dutch  Indian  Government  were,  of  course,  directed  to  taking 
measures  for  the  safety  and  relief  of  the  survivors  of  this  terrible  catastrophe,  and 
for  restoring  the  navigation  of  the  great  marine  highway  between  Java  and  Sumatra.  A 
man-of-war  was  despatched  to  the  Strait  to  visit  the  ports,  and  penetrate  as  far  as  pos- 
sible into  the  great  bays  on  both  sides  of  the  Strait ;  while  a  surveying  vessel  was  ordered 
to  make  first  a  preliminaiy  and  then  a  detailed  examination  of  the  changes  which  had 
taken  place,  and  which  had  rendered  the  existing  charts  almost  useless.  But  no  sooner 
was  this  accomplished,  than  the  Government  determined  to  undertake  a  complete 
scientific  investigation  into  the  effects  of  the  eruption,  and  of  the  phenomena  which 
accompanied  it,  as  far  as  these  could  be  ascertained  by  the  inquiries  of  a  Commission 
visiting  the  whole  of  the  district  chiefly  affected  by  it.  The  Dutch  Indian  Govern- 
ment were  fortunate  in  having  at  their  disposal  the  services  of  the  eminent  geologist, 
Mr.  R.  D.  M.  Verbeek,  whose  surveys  of  Java,  Sumatra,  and  of  the  actual  scene 
of  the  outbreak,  are  widely  known  to  the  scientific  world.  The  Dutch  Scientific 
Commission,  for  inquiry  into  the  nature  and  results  of  the  Krakatoa  eruption,  was 
appointed  on  October  the  4th,  1883  ;  a  preliminary  report  of  its  proceedings  appeared 
on  February  the  19th,  1884  ;*  and  subsequently,  the  complete  report,  illustrated  by 
an  atlas  of  plates,  and  containing  a  very  valuable  permanent  record  of  the  event,  was 
published  in  both  the  Dutch  and  the  French  languages.t 

At  the  commencement  of  1884,  the  French  Minister  of  Public  Instruction,  on 
the  motion  of  the  *'  Commission  des  Voyages  et  Missions,"  directed  MM.  K£n£  Br6on 
and  W.  C.  Korthals  to  visit  the  scene  of  the  eruption,  and  to  make  a  report  as  to  the 
result  of  their  enquiries  upon  the  spot.  Only  a  preliminary  report  of  this  Comnais- 
sion,  dated  May  the  30th,  1884,  has  yet  been  published,^  but  an  interesting  accoimt 

♦  *  Kort  verslag  over  de  uitbarsting  van  Krakatau,'  door  R.  D.  M.  Verbbek. 

t  *  Krakatan,  par  R.  D.  M.  Verbbek,  Ing^nienr  en  clief  des  Mines,  Chevalier  du  Lion  N^erlandais. 
Public  I)ar  ordre  de  son  Excellence  le  Gouvernenr- General  des  Indes  N^rlandaises.'  Batavia.  The  first 
part  of  the  Datch  edition  appeared  in  1884,  and  o£  the  French  in  1885.  The  second  part  appeared  in 
Dutch  in  1885,  and  in  French  in  1886. 

+  '  Comptes  Rendus,'  torn,  xcix.,  p.  395. 


PROF.  JUDD  ON  THE  VOLCANIC  PHENOMENA.  3 

of  the  proceedings  of  its  members,  from  the  pen  of  M.  Bk^n,  has  appeared  in  a 
French  periodical.* 

The  Sunda  Strait,  where  this  great  convulsion  occurred,  connecting,  as  it  does, 
the  China  Seas  with  the  Indian  Ocean,  is  one  of  the  most  important  commercial 
highways  of  the  globe,  and  many  hundreds  of  vessels  pass  through  it  every  year. 
During  the  time  that  the  eruption  of  Krakatoa  was  in  progress,  a  niunber  of  ships 
passed  within  sight  of  the  volcano,  and  even  at  the  crisis  of  the  eruption  several 
vessels  were  actually  within  the  Strait,  while  others  were  in  its  immediate  proximity. 
The  observations  made  by  captains  or  passengers  in  these  vessels,  as  well  as  in  others 
at  greater  distances,  and  recorded  in  log-books,  diaries,  letters  to  journals,  &c,,  are  of 
very  great  value  and  interest ;  for,  those  on  shipboard  were  not  exposed  to  the  dangers 
incurred  by  the  witnesses  on  the  land,  seeing  that  the  destructive  sea-waves  passed 
harmlessly,  and  in  some  cases  unobserved,  by  them.  Inasmuch,  however,  as  many 
months  had  to  elapse  before  these  ships  could  reach  the  various  ports  of  Europe  and 
America  to  which  they  were  bound,  it  was  long  before  all  the  facts  and  observations 
could  be  collected  and  compared.  The  members  of  the  Krakatoa  Committee  of  the 
Royal  Society  are  under  great  obligations  to  the  numerous  captains  and  owners  of 
merchant  vessels,  who,  in  response  to  an  appeal  made  by  them  through  the  '  Times '  and 
other  newspapers,  have  furnished  them  with  copies  of  logs  and  other  documents, 
and  with  specimens  of  pumice  and  dust  collected  at  a  great  niunber  of  different 
points. 

To  those  who,  like  Herr  Metzger,  of  Stuttgart,  and  Dr,  Kloos,  of  Carlsruhe, 
have  collected  from  Dutch  and  other  newspapers  statements  bearing  upon  the 
eruption,  and  to  journals  which  have  opened  their  columns  to  correspondence  on  the 
subject,  the  Committee  is  likewise  indebted  for  many  interesting  details  which  might 
otherwise  have  been  lost.  Very  great  value  attaches  to  the  mass  of  useful  materials 
collected  in  the  pages  of  '  Nature '  during  the  months  which  followed  the  eruption. 
To  Mr.  H.  O.  Forbes,  also,  who  was  at  Batavia  after  the  commencement  of  the 
eruption,  and  who  took  much  pains  in  collecting  information  bearing  on  the  subject,  t 
the  Committee's  thanks  are  largely  due. 

The  whole  of  the  circumstances  attending  the  great  catastrophe  of  the  Sunda 
Strait  have  been  so  carefully  investigated,  and  so  faithfully  recorded  by  Mr.  Verbeek, 
in  his  able  and  comprehensive  work,  *  Krakatau,'  that  it  will  only  be  necessary  in  the 
present  part  of  this  report  to  give  a  general  srunmary  of  the  order  of  events,  dwelling 
especially  upon  those  questions  a  right  understanding  whereof  is  necessary  for  the 
interpretation  of  the  remarkable  phenomena  displayed  in  distant  countries,  which 
in  the  following  parts  of  the  report  are  shown  to  have  been  more  or  less  directly 
connected  with  the  volcanic  disturbance  at  Krakatoa. 

The  scene  of  this  terrible  catastrophe  lies  in  the  very  heart  of  the  district  which 

♦  '  La  Nature,'  April  4  and  25,  and  May  16,  1885. 

t  '  Proceedings  of  the  Royal  Geographical  Society,'  vol.  vi.  (1884),  p.  129. 

B   2 


PROF.  JUDD  ON  THE  VOLCANIC  PHENOMENA. 


has  long  been  recognised  as  being  at  the  present  epoch  the  greatest  focus  of  volcanic 
activity  upon  the  globe.  The  Island  of  Java,  with  an  area  about  equal  to  that  of 
England,  contains  no  fewer  than  forty-nine  great  volcanic  mountains,  some  of  which 
rise  to  a  height  of  12,000  feet  above  the  sea-level.  Of  these  volcanoes,  more  than 
half  have  been  seen  in  eruption  during  the  short  period  of  the  European  occupa- 
tion of  the  island,  while  some  are  in  a  state  of  almost  constant  activity.  Hot 
springs,  mud-volcanoes,  and  vapour- vents  abound  in  Java,  while  earthquakes  are  by 
no  means  unfrequent.  The  chain  of  volcanoes  which  runs  through  the  whole  of  Java 
is  continued  in  Sumatra  on  the  west,  and  in  the  islands  of  Bali,  Lombok,  Sumbawa, 
Flores,  and  Timor  on  the  east. 

The  marked  linear  arrangement  in  this  immense  chain  of  volcanic  moimtains 
points  to  the  existence  of  a  great  fissure  in  the  earth's  (;rust,  along  which  the  subter- 
ranean energy  has  been  manifested.  The  Strait  of  Sunda,  which  separates  Java  from 
Sumatra,  is  a  shallow  one,  having  a  depth  of  rarely  more  than  100  fathoms.  Along 
the  line  of  this  Strait  we  have  evidence  of  a  transverse  fissure  crossing  the  main 
one  nearly  at  right  angles  {See  Fig.  1).     Upon  this  transverse  fissure  a  number  of 


SUMATRA 


Fig.  1. — Sketch-map  of  the  Sunda  Strait,  showing  the  lines  of  volcanic  fissure  which  appear  to  traverse 

the  district. 


'N 


PROF.  JUDD  ON  THE  VOLCANIC  PHENOMENA.  5 

volcanoes  have  been  thrown  up,  namely — Pajung,  in  Java,  with  a  height  of  1,500  feet ; 
the  cone  of  Princes  Island,  1,450  feet ;  Krakatoa,  2,623  feet ;  Sebesi,  2,825  feet ;  and 
Bajah  Bassd,  in  Sumatra^  4,398  feet. 

In  spite  of  the  significance  of  its  position  at  the  point  of  intersection  of  these 
two  great  lines  of  volcanic  fissure,  Krakatoa  had,  until  the  year  1883,  attracted  but 
little  attention.  Amid  so  many  volcanoes  of  more  striking  appearance  and  more 
firequent  activity,  it,  in  fact,  remained  almost  unnoticed. 

Krakatoa  does  not  present  the  regularly  conical  outlines  characteristic  of 
volcanoes,  a  form  which  is  so  well  exhibited  by  the  neighbouring  island  of  Sebesi  (See 
Fig.  2) ;  it  is,  indeed,  only  a  fragment  of  a  great  crater-ring  rising  out  of  the  Sunda 


Fig.  2,— Sketch  of  the  Island  of  Sehesiy  as  seen  from  the  north-east  (after  Verheek), 

Strait.  The  general  relations  of  the  islands  of  the  Krakatoa  group  and  the  outlines 
which  they  exhibited  prior  to  the  great  eruption  are  illustrated  by  the  accompanying 
sketch-map  and  section  (Figs.  3  and  4,  page  6). 

By  the  great  eruption  of  August,  1883,  the  volcano  of  which  Krakatoa  and  the 
adjoining  islands  form  parts  was  completely  eviscerated.  The  admirable  descriptions 
given  by  MM.  Verbeek  and  Br£on  of  the  splendid  sections  now  exposed  enable  us 
not  only  to  determine  the  nature  of  its  materials,  but  to  study  all  the  details  of  the 
internal  structure  of  the  volcanic  mass.  Guided  by  the  principles  which  have  been 
established  by  the  study  of  numerous  volcanoes  in  different  stages  of  their  develop- 
ment, we  are  able  from  the  data  thus  obtained  to  re-construct  the  whole  history  of 
this  interesting  example  of  volcanic  architecture. 


I. — Sketch  of  the  History  op  the  Volcano  of  Krakatoa. 

No  principle  of  vulcanology  is  better  established  than  that  of  the  alternation, 
in  the  history  of  most  volcanoes,  of  periods  during  which  constant  ejections  take  place, 
whereby  great  mountain  masses,  having  the  beautiful  conical  forms  characteristic 
of  Chimborazo  and  Fusiyama,  are  slowly  and  gradually  built  up,  and  of  violent 
paroxysms,  by  which  in  the  course  of  a  comparatively  short  period,  the  whole  centre 
of  the  great  volcanic  mass  is  blown  away,  and  scattered  in  the  form  of  scorisB  and 
dust ;  only  the  lowest  and  peripheral  part  being  left  behind  in  the  form  of  a  crater- 
ring,  or  "  basal  wreck,"  as  Darwin  so  aptly  called  the  ruins  of  an  eviscerated 
volcano. 


PROF.  JUDD  ON  THE  VOLCANIC  PHENOMENA. 


The  great  volcanic  mountain,  of  which  Krakatoa,  Verlaten  Island,  Lang  Island, 
and  Polish  Hat  are  portions  of  a  basal  wreck  rising  above  the  waters  of  the  ocean, 


SEBESI    CHANNEL 


VERLATEN 


*     r 

•mite  Rock 


KRAKATOA  I.C 


LAKOJ. 


<*>^ 


GREAT     CHANNEL 


I       7       I 


En^UsK  Miles. 


Fig.  3. — Map  of  the  islands  of  the  Krakatoa  Group  before  the  eruption  (from  the  Admiralty  Chart) .     The 
nearly  circular  line indic<ites  approximately  the  submerged  edge  of  the  great  crater, 

Rakafa 
««f»  ft 


VerlaWl 


Stream 


9is:iian^ 


Fig.  4. — Outline'Section  viewed  from  south-west  showing  the  position  of  the  volcanic  cones  upon  the  Island  of 

Krakatoa  previous  to  the  eruption, 

must  have  origiually  been  one  of  considerable  dimenBions.  Its  circumference  at  what 
is  now  the  sea-level  could  not  have  been  much  less  than  twenty-five  miles,  and  its 
height  above  the  same  datiun  plane  was  perhaps  not  less  than  10,000  to  12,000  feet ; 
so  that,  as  might  have  been  expected  from  its  position  at  the  intersection  of  two  great 
earth-fissures,  this  volcanic  cone  must  have  rivalled  in  its  dimensions  the  largest  among 
the  volcanoes  of  the  East -Indian  Archipelago.  The  general  form  of  the  volcano  at 
this  period  of  its  history  is  illustrated  in  Fig.  5. 

That  this  great  volcanic  mountain  was  entirely  built  up  by  eruptions  which  have 


PROF.  JUDD  ON  THE  VOLCANIC  PHENOMENA.  7 

taken  place  in  very  recent  times,  geologically  speaking,  is  shown  by  an  interesting 
fact  which  has  been  ascertained  by  Mr.  Verbeek,  namely,  that  beneath  the  mass  of 
materials  of  which  the  volcano  is  composed  there  occur  deposits  of  post-tertiary  age, 
and  that  these  in  turn  rest  on  the  widely  distributed  tertiary  rocks  which  are  so 


Fig.  5. — Probable  outlines  of  the  Volcano  of  KraTcatoa^  at  the  period  of  its  maximum  dimensions. 

well  known  in  Java,  Sumatra,  and  the  adjoining  islands.  The  original  volcano,  as  far 
as  can  be  judged  by  the  fragments  which  remain  of  it,  appears  to  have  been  almost 
entirely  built  up  of  lava-streams  of  the  remarkably  interesting  rock  known  as 
enstatite-dacite,*  consisting  of  the  same  minerals  which  characterise  the  andesitic 
lavas  so  abundant  in  Java  and  Sumatra ;  it  nevertheless  differs  from  the  bulk  of  these 
by  the  higher  percentage  of  silica  which  it  contains.  During  the  outwellings  of  these 
massive  lavas  there  is  scarcely  any  trace  of  explosive  action  on  any  considerable  scale 
having  taken  place,  and  few,  if  any,  tuffs  were  produced. 

At  some  unknown  period  this  volcano  became  the  scene  of  an  eruption,  or  series 
of  eruptions,  which,  judging  from  the  effects  they  have  produced,  must  have  been  on 
even  a  far  grander  scale  than  that  which  four  years  ago  attracted  so  much  interest. 
By  these  outbursts  the  whole  central  mass  of  the  volcano  seems  to  have  been  blown 
away,  and  only  an  irregular  crater-ring  left  behind.  The  gi-eat  crater  thus  formed 
must  have  had  a  diameter  of  three  or  four  miles,  and  its  highest  portions  could  have 
risen  but  a  few  hundreds  of  feet  above  the  present  level  of  the  sea.     (See  Fig.  6,  p.  8.) 

The  next  stage  in  the  history  of  the  volcano  consisted  in  the  gradual  filling  up 
of  the  crater  by  a  series  of  comparatively  quiet  eruptions,  taking  place  at  the  bottom 
of  the  crater-ring,  and  building  up  small  volcanic  cones  within  it.  By  this  means  the 
crater  was,  to  a  great  extent,  filled  up,  and  portions  of  it  raised  above  what  is  now  the 
sea-level.  [See  Fig.  7,  p.  8).  Whether  the  tract  now  constituting  the  Strait  of  Sunda 
was  then  dry  land  imiting  the  present  islands  of  Java  and  Sumatra  we  have  no  means 
of  determining ;  but  I  may  point  out  that  there  are  some  grounds  for  believing  that 

♦  This  rock  lias  been  called  by  many  authors  **  enstatite-  "  or  "  hypersfcliene-andesite ;  "  but  although 
the  minerals  present  in  the  rocks  are  the  same  as  those  found  in  the  *'  enstatite-andesites  "  it  has  a 
silica-percentage  of  over  70,  and  it,  therefore,  belongs  to  the  class  of  acid  lavas.  It  bears,  in  fact,  the 
same  relation  to  the  andesites  that  the  rhyolites  do  to  the  trachytes,  and  on  this  account  the  name 
"  dacite  "  may  be  convenieutly  applied  to  it. 


8 


PROF.  JUDD  ON  THE  VOLCANIC  PHENOMENA. 


the  formation  of  the   depression   occupied    by    the  straits  was  subsequent  to  the 
evisceration  of  the  volcano. 

In  a  great  number  of  cases  it  has  been  shown  that  the  piling  up  of  materials 
upon  a  portion  of  the  earth's  crust  to  form  volcanic  mountains  is  accompanied  or 


FiQ.  6. — Probable  outlines  of  the  great  crater-ring  ("  basal  wreck  '*)  of  the  Krakatoa  VolcanOy  after  the 
ancient  paroxysmal  outbursts.     The  dotted  line  indicates  the  mass  which  was  blown  away. 

followed  by  a  depression  of  the  surface,  so  that  the  strata  all  round  the  volcano 
acquire  a  downward  dip  towards  the  centre  of  eruption.*  The  cause  of  this  depres- 
sion of  the  volcanic  mass  appears  to  be  iwofo\(i— first,  the  removal  of  the  support 
afforded  by  the  vast  masses  of  material  removed  from  below  the  vent  during  erup- 
tions ;  and,  secondly^  the  weight  of  the  gradually  increasing  mountain-mass  which 


Fig.  7. — Trobable  outlines  of  the  Krakatoa  Volcano  after  the  great  crater  indicated  by  the  dotted  line  had 
been  filled  up  by  the  growth  of  numerous  small  cones  within  it. 

rests  on  the  flexible  crust.  It  seems  not  improbable  that  the  depression  between  the 
islands  of  Java  and  Sumatra  may  have  resulted  from  subsidences  accompanying  or 
following  the  ejections  taking  place  at  the  great  central  volcanic  focus  of  Krakatoa. 

Subsequently  to  the  partial  in-filling  of  the  great  crater,  a  lateral  or  parasitical 
eruption  seems  to  have  taken  place  on  the  southern  edge  of  the  great  crater-ring,  and 
this  outburst  is  remarkable  for  a  very  striking  change  in  the  nature  of  the  materials 
ejected.  The  materials  forming  the  cones  inside  the  crater-ring  were  composed  of 
materials  similar  to  that  of  the  latter  itself,  namely,  the  lava  known  as  enstatite- 
dacite,  but  the  new  parasitical  cone  was  built  up  of  basaltic  lavas  and  scoriae.  The 
ejections  from  this  lateral  vent  must  have  been  abundant  and  long-continued,  for  they 

♦  Darwin,  *  Volcanic  Islands,'  p.  9 ;  Heaphy,  *  Qnart.  Journ.  Geol.  Soc.,'  vol.  xvi.  (1800),  p.  244 ;  Scrope, 
'Volcanoes,'  2ud  ed.  (1872),  p.  225;  and  the  author,  *  Quart.  Journ.  Geol.  Soc.,'  vol.  xxx.  (1874),  p.  257. 


PROF.  JUDD  ON  THE  VOLCANIC  PHENOMENA.  9 

resulted  in  the  piling  up  of  a  cone  which,  standing  on  the  edge  of  the  old  crater-ring, 
rose  to  the  height  of  2,623  feet  above  the  sea.     (Fig.  8.) 

N.W.  y^-V  S.E. 


Fig.  8. — Form  of  KraJeatoa  in  historical  timesy  after  the  formation  of  the  great  lateral  cone  of  Bakata,^  and 

the  growth  of  other  cones  within  tJie  great  crater. 

It  was  this  conspicuous  basaltic  cinder-cone  that  was  called  by  the  natives  the 
peak  of  Bakata,  which  in  the  old  Kawi  or  Javanese  language  signifies  a  crab.  The 
name,  under  the  Dutch  form,  Krakatau,  the  Portuguese  KrakatSo,  and  the  English 
Krakatoa,  has  been  extended  to  the  whole  island  on  which  this  striking  cinder-cone 
stood.  It  is  convenient  to  employ  the  same  name  also  for  the  entire  volcano  of  which 
this  island  constitutes  the  largest  part  rising  above  the  ocean. 

Amid  the  numerous,  lofty,  and  strikingly  conical  volcanic  mountains  of  this 
district,  the  insignificant  masses  of  Krakatoa  and  its  neighbouring  islets  naturally 
attracted  but  little  attention.  The  early  voyagers  in  these  seas  describe  the  four 
small  islands  of  the  group,  like  the  others  in  the  Strait,  as  being  clothed  with  the  most 
luxuriant  vegetation,  and  as  affording  a  wonderful  relief  to  eyes  long  accustomed  to 
the  monotony  of  a  waste  of  waters.  None  of  the  islands  of  the  Krakatoa  group 
appears  to  have  had  at  any  time  permanent  inhabitants.  The  natives  living  in  the 
towns  and  villages  along  the  shores  of  the  Strait  merely  visited  the  islands  from  time 
to  time,  in  order  to  collect  the  produce  of  the  magnificent  forests  which  covered  them ; 
while  the  anchorages  and  places  of  shelter  around  their  shores  were  resorted  to  by 
the  native  fishermen.  Consequently,  while  hundreds  of  vessels  every  year  passed 
within  a  short  distance  of  these  remarkable  islands,  the  characters  of  their  interior 
remained  almost  unknown ;  indeed,  such  phenomena  as  the  outbm'st  of  hot  springs 
and  the  occurrence  of  earthquake-shocks  might,  and  probably  did,  occiir  without 
attracting  attention,  although  the  outbreak  of  any  considerable  volcanic  eruption  would 
have  given  rise  to  steam-clouds  that  could  not  fail  to  attract  the  attention  of  those 
on  board  passing  vessels. 

Unfortunately,  neither  the  Dutch  nor  the  English  charts  give  any  very  exact 
details  concerning  the  forms  and  contours  of  the  islands.  The  two  great  channels  to 
the  north  and  south  of  the  Krakatoa-group  were  carefully  sounded,  but  of  the  islands 
themselves  we  have  only  the  outlines  rudely  laid  down  (and  these  differ  very  greatly 
in  the  several  published  charts),  with  sketches  of  their  form  as  seen  from  ships,  and 
indications  of  their  heights  above  the  sea-level.  A  sketch  of  the  island  of  Krakatoa 
was  made  by  P.  J.  Buijskes,  the  captain  of  a  Dutch  man-of-war,  in  1849,  and  another 
drawing  of  the  islands  of  the  group  by  Mr.  Verbeek  in  1880.  The  English  chart,  with 
sketches  of  some  of  the  islands  as  seen  from  the  sea,  was  made  in  1854,  and  the 
Dutch  chart  in  1874;  but  additions  and  corrections  to  both  these  charts  were  made 

c 


10  PROF.   JUDD   ON    THE   VOLCANIC    PHENOMENA. 

from  time  to  time  by  the  surveying  officers  of  both  navies  Nothing,  however,  in 
the  shape  either  of  a  complete  topographical  or  of  a  geological  survey  of  the  islands 
was  ever  undertaken ;  and  the  absence  of  the  information  which  would  have  been 
aiforded  by  such  surveys,  is  very  seriously  felt  in  all  attempts  to  estimate  the  exact 
nature  and  amount  of  the  changes  wrought  by  the  late  eniption. 

From  all  the  information  available,  it  appears  that  Krakatoa  consisted  of  the  regular 
basaltic  cone  known  as  Rakata,  rising  from  the  southern  end  of  the  island  to  the 
height  of  2,623  feet,  and  having  a  small  depression,  probably  marking  a  crater,  at  its 
summit.  The  northern  part  of  the  island  seems  to  have  consisted  of  a  number  of 
more  or  less  regularly  conical  masses,  two  of  which  only  had  received  distinct  names. 
Near  the  centre  of  the  island  was  the  cone  called  Danan,  and  this,  or  a  neighbouring 
peak,  had  a  height  of  1,496  feet,  and  is  said  to  have  had  a  crater  at  its  top ;  at  the 
northern  end  of  Krakatoa  was  the  smaller  cone  called  Perboewatan,  with  a  height  of 
399  feet,  having  a  crater  breached  on  its  western  side,  fi'om  which  a  stream  of  very 
glassy  enstatite-dacite  lava  descended  to  the  sea-level.  Verlaten  and  Lang  Islands 
were  isolated  portions  of  the  old  crater-ring,  and  rose  to  only  a  moderate  elevation 
above  the  sea-level,  while  Polish  Hat  formed  part  of  the  masses  ejected  within  the 
crater.     {See  Figs,  3  and  4,  p.  6,) 

The  native  traditions  collected  by  M.  BntoN  point  to  the  conclusion  that  eruptions 
had  taken  place  at  Krakatoa  during  the  time  that  the  district  had  been  inhabited  by 
the  Malayan  tribes.  Authentic  history  in  this  case,  however,  commences  only  about 
three  centuries  ago. 

In  May,  1680,  an  eruption  appears  to  have  broken  out  at  Krakatoa,  of  which  we 
have  unfortunately  only  very  meagre  accounts  in  the  wi^itings  of  Vogel  and  Hesse. 
Great  earthquakes  are  said  to  have  been  felt  in  the  neighbourhood,  and  vast  quantities 
of  pumice  to  have  been  ejected,  which  covered  all  the  surrounding  seas.  The  eruption 
seems  to  have  continued  with  little  intermission  till  the  November  of  the  following 
year,  and  to  have  destroyed  the  rich  tropical  forests  that  covered  the  island.  Which 
of  the  volcanic  cones  composing  Krakatoa  was  then  in  eruption  is  not  certainly  known, 
but  it  may  be  plausibly  conjectured  that  it  was  Perboewatan,  upon  the  slopes  of  which 
conspicuous  and  very  fresh  lava-streams  of  enstatite-dacite  are  recorded  as  being  seen 
by  seyeraj  later  authors.  The  eruption  at  this  time  seems  to  have  been  of  the 
conitiinual  moderate  character  by  the  repetition  of  which  the  small  cones  occupying  the 
grea{ter  part  of  Krakatoa,  and  filling  up  the  vast  submerged  crater,  had  been  formed 

From  the  effects  of  this  outburst,  however,  Krakatoa  soon  recovered,  and  the 
evei>i;  smms  to  have  been  so  far  forgotten  that  doubts  have  even  been  expressed  as  to 
the  accura^jy  of  the  narratives  recording  it.  For  these  doubts  there  do  not  seem  to 
be  any  very  good  reasons.  The  rich  vegetation  which  clothed  the  island  made  the 
inhabitants  of  the  neighbouring  shores  and  the  passers  in  ships  forget  the  terrible 
forces  which  were  slumbering  beneath  a  scene  of  so  much  beauty.  Some,  however, 
who  landed  on  the  island  and  made  their  way  into  the  almost  impenetrable  forests 


PROF.   JUDD   ON   THE   VOLCANIC   PHENOMENA,  11 

declared  that  they  had  met  with  hot  springs,  and  one  such  spring  is  indicated  on  the 
Admiralty  chart  of  the  island. 

Six  or  seven  years  ago  it  became  evident  that  the  volcanic  forces,  which  for 
nearly  two  centuries  had  remained  dormant  beneath  the  Sunda  Strait,  were  once  more 
awakening  into  activity.  Earthquakes  were  of  frequent  occurrence,  and  during  one 
of  these,  on  September  the  1st,  1880,  the  lighthouse  on  Java's  First  Point  was 
seriously  injured.     These  earthquakes  were  felt  as  far  away  as  North  Australia. 

On  the  morning  of  Sunday,  May  the  20th,  1883,  booming  sounds  like  the  firing 
of  artillery  were  heard  at  Batavia  and  Buitenzorg,  which  towns  are  situated  nearly 
100  English  miles  from  Krakatoa,  and  for  many  hours  a  rattling  of  the  doors  and 
windows  was  maintained  in  these  towns  and  in  all  the  neighbouring  villages ;  on' 
board  a  mail-steamer  passing  through  the  Strait,  it  was  noticed  that  the  compass- 
needles  were  violently  agitated. 

On  the  morning  of  May  the  21st  a  sprinkling  of  ashes  was  noticed  to  fall  at 
Telok  Betong  and  Semanka,  on  one  side  of  the  Strait,  and  at  Buitenzorg  and  the 
mountains  around  that  place  on  the  other.  But  it  was  not  till  the  evening  of  the 
same  day  that  a  steam-column,  issuing  from  Krakatoa,  revealed  to  the  inhabitants  of 
the  district  the  true  locality  of  the  disturbance  which  had  been  going  on  for  two  days. 
On  the  22nd  of  May,  at  8  p.m.,  the  captain  of  a  vessel  passing  close  to  Krakatoa  was 
able  to  see  that  the  dome-shaped  mass  of  vapour  issued  from  the  lower  parts  of  the 
island,  and  not  from  the  top  of  the  peak  of  Bakata  ;  a  succession  of  fiery  flashes,  each 
followed  by  a  loud  explosion,  accompanied  the  discharge  of  fragments  of  pumice  and 
dust  into  the  atmosphere,  while  vivid  flashes  of  lightning  were  seen  playing  around 
the  vapour-column.  Much  of  the  pumice  and  dust  fell  beyond  the  limits  of  the 
island,  and  on  May  the  23rd  a  ship  encountered  a  large  quantity  of  this  pumice  off" 
Flat  Cape,  in  Sumatra,  which  was  found  to  increase  in  amount  until  Krakatoa  was 
passed.     The  pumice  was  then  floating' out  into  the  Indian  Ocean. 

It  is  evident  from  these  accounts  that  Krakatoa  had  re-entered  on  a  phase  of 
moderate  (Strombolian)  activity,  similar  to  that  which  it  had  exhibited  for  some 
months  during  the  years  1680  and  1681.  That  the  outburst  was  one  of  considerable 
violence,  however,  especiaUy  at  its  commencement,  was  shown  by  the  fact  that  the 
commander  of  the  German  war- vessel,  Elisabeth,  estimated  the  height  of  the  dust- 
column  issuing  from  the  volcano  as  11  kilometres  (36,000  feet,  or  7  miles) ;  and  falls 
of  dust  were  noticed  at  the  distance  of  300  miles. 

Mr.  H.  O.  Forbes,  then  resident  at  Timor,  1,350  English  miles  distant,  relates 
that  on  May  the  24th  a  small  quantity  of  greyish  dust  fell  there  ;  but  it  is  possible 
that  this  may  have  come  from  some  other  and  much  nearer  volcano  than  Krakatoa. 

It   seems  that  the  eruption,  which  was  so  violent  at  its  first  outburst,  soon 

became  of  a  more  moderate  character — so  much  so,  indeed,  that  the  residents  in 

Batavia  and  other  portions  of  the  surrounding  district,  who  are  accustomed  to  hearing 

of  earthquakes  and  volcanoes  in  their  vicinity,  soon  ceased  to  pay  much  attention 

c  2 


12  PROF.  JUDD   ON   THE   VOLCANIC   PHENOMENA. 

to  the  subject.  Mr.  Yerbeek  has,  however,  collected  from  the  lighthouse-keepers  on 
the  shores  of  the  Strait,  and  from  the  captains  of  the  mail-steamers  and  other  passing 
vessels,  many  very  interesting  details  of  this  preliminary  outbreak. 

On  May  the  26th  an  excursion  party  was  formed  at  Batavia,  and  proceeded 
in  a  steam-vessel  to  the  scene  of  the  eruption.  They  reached  the  volcano  on  the 
Sunday  morning.  May  the  27th,  after  witnessing,  during  the  night,  several  tolerably 
strong  explosions,  which  were  accompanied  by  earthquake-shocks.  Krakatoa  and  the 
adjoining  islands  were  seen  to  be  covered  with  fine  white  dust  like  snow,  while  the 
trees  on  the  northern  parts  of  Krakatoa  and  Verlaten  Islands  had  been,  to  a  great 
extent,  deprived  of  their  leaves  and  bmnches  by  falling  pumice— =-a  fate  which  those 
on  Lang  Island  and  Polish  Hat,  as  well  as  on  the  Peak  of  Rakata,  had  to  a  great 
extent  escaped. 

It  was  then  seen  that  it  was  the  cone  of  Perboewatan  which  was  in  activity — 
explosions  occurring  at  intervals  of  from  5  to  10  minutes,  and  each  of  these  explosions 
being  attended  with  the  uncovering  of  the  liquid  lava  in  the  vent,  whereby  the  over- 
hanging steam-cloud  was  lighted  up  and  glowed  for  a  few  seconds.  The  column  of 
vapour  was  estimated  as  rising  to  a  height  of  less  than  10,000  feet,  and  the  fragments 
of  pumice  as  being  shot  to  the  height  of  about  600  feet.  It  appears  from  these 
accounts  that  the  violence  of  the  eruption  had  somewhat  diminished  since  the  first 
detonations,  which  were  heard  so  far  off  and  were  accompanied  by  so  lofty  a  vapour- 
cloud.  From  some  of  the  accounts,  however,  it  appears  that  certain  of  the 
explosions  were  of  exceptional  violence,  and  that  pieoes  of  pumice  were  thrown  to 
very  great  heights  in  the  atmosphere ;  for  it  is  said  that  they  were  caught  by  the 
upper  currents  of  the  air  and  carried  away  in  a  direction  opposite  to  that  towards 
which  the  wind  was  blowing  at  the  time.  The  noise  made  by  the  explosions  and  the 
hurtling  of  the  ejected  fragments  in  the  air,  is  said  to  have  been  so  great  that  when 
a  rifle  was  discharged  its  sound  might  be  compared  to  "  the  popping  of  a  champagne-, 
cork  amid  the  hubbub  of  a  banquet." 

Ascending  ankle-deep  in  loose  pumice  over  the  slopes  of  the  low  depressed  cone 
of  Perboewatan,  which  was  found  to  have  a  height  of  something  over  300  feet  above 
the  sea,  the  visitors  to  the  island  found  at  the  top  a  large  crater  8,000  feet  in 
diameter,  and  sloping  down  to  a  flat  bottom  which  had  about  one-half  that  diameter, 
and  was  covered  with  a  black  crust.  The  crater-floor,  which  was  about  150  feet  from 
the  upper  edge,  showed  in  its  centre  a  cavity  about  150  feet  in  diameter,  from  which 
the  great  steam-column  issued  with  a  terrific  sound.  The  western  side  of  the  crater 
was  seen  to  be  breached  by  the  obsidian  lava-stream  descending  to  the  sea.  It  is 
conjectured  that  this  was  formed  in  1680-81. 

The  material  ejected  was  pumice  with  fragments  of  black  glass ;  it  is  desci-ibed 
by  some  as  containing  crystals  of  plagioclase  felspar,  pyroxene  and  magnetite.  A 
specimen  brought  away  by  one  of  the  visitors  was,  however,  given  to  Mr.  H.  O, 
Forbes,  and  by  him   brought  to  England ;  and  this  specimen,  which  was  handed 


PROF.   JUDD   ON   THE   VOLCANIC   PHENOMENA.  13 

to  me  by  that  gentleman,  proved  to  be  of  a  somewhat  peculiar  character  and  quite 
different  from  most  of  the  pumice  ejected  during  the  later  stages  of  the  eruption,  as 
will  be  shown  in  the  sequel. 

A  photographer  on  board  the  steamer  succeeded  in  obtaining  a  satisfactory  view 
of  the  eruption  at  that  time,  and  this  photograph,  which  was  coloured  by  an  eye- 
witness of  the  eruption,  is  reproduced  in  Plate  I. 

After  the  period  of  this  visit,  although  there  was  no  intermission  in  the  eruption, 
there  appeared  to  be  a  decline  in  the  volcanic  activity,  as  far  as  can  be  judged  from 
the  reports  obtained  from  the  lighthouses  of  the  Strait,  and  from  the  captains  of 
passing  vessels.  It  was  ascertained  at  Anjer  on  June  the  19th,  that  the  height  of  the 
vapour-column  and  the  force  of  the  explosions  were  again  increasing ;  and  on  the  24th 
of  the  same  month  it  was  distinctly  noticed  that  a  second  column  of  vapour  was  ascend- 
ing from  the  centre  of  the  island.  At  Katimbang,  from  which  place  the  Island  of 
Krakatoa  can  be  seen,  it  was  noticed  that  the  appearance  of  Perboewatan  had  entirely 
changed ;  the  conspicuous  summit  had  disappeared,  having  probably  been  blown  away 
during  the  enlarging  and  deepening  of  the  crater. 

During  the  month  of  July,  the  eruption  from  the  two  points  in  the  island  was 
observed  and  described,  both  by  witnesses  on  the  shores  and  by  others  on  vessels 
making  the  passage  of  the  Strait.  Some  detonations  of  exceptional  violence,  and 
several  small  earthquakes,  were  from  time  to  time  recorded  alike  from  the  Java  and 
Sumatra  shores ;  but  in  a  district  where  earthquakes  and  volcanic  outbursts  are  so 
frequent,  this  eruption  of  Krakatoa  during  the  summer  months  of  1883  seems  to 
have  been  regarded  as  nothing  more  than  a  nine-days'  wonder,  and  soon  ceased  to 
attract  any  particular  attention. 

On  August  the  11th,  however,  the  island  was  visited  by  Captain  Ferzenaar,  the 
chief  of  the  topographical  staff  of  Bantam.  Sailing  along  the  north-east  side  of  the 
island  in  a  native  boat  he  was  able  to  make  a  sketch  of  that  part  of  the  island,  the 
heavy  masses  of  vapour  and  dust  driven  by  the  wind  preventing  him  from  examining 
the  other  portions  of  the  island  By  this  time  the  forests  of  the  whole  of  Krakatoa 
appear  to  have  been  completely  destroyed,  only  a  few  trunks  of  trees  being  left 
standing  above  the  thick  covering  of  pumice  and  dust.  This  mantle  of  dust  near  the 
shores  W£U9  found  to  be  20  inches  in  thickness. 

Three  large  vapour-columns  were  seen  ascending  and  carrying  up  immense  clouds 
of  dust  and  pumice  from  as  many  craters,  one  of  these  being  the  original  crater  of 
Perboewatan,  while  the  other  two  were  in  the  centre  of  the  island.  Of  the  latter,  one 
was  probably  the  original  crater  of  Danan,  enlarged  and  deepened  by  the  explosive 
action  so  as  to  diminish  the  height  of  the  cone,  while  the  other  crater  seems  to  have 
been  opened  at  the  northern  foot  of  Danan.  But  besides  these  three  principal 
craters  no  fewer  than  eleven  other  foci  of  eruption  could  be  observed  on  the  visible 
portions  of  the  island,  from  which  smaller  steam-columns  issued  and  ejections  of 
dust  took  place. 


14  PROF.   JUDD   ON   THE  VOLCANIC    PHENOMENA. 

It  is  evident,  therefore,  that  at  this  period  the  activity  of  the  volcanic  forces  in 
the  island  had  increased  in  a  remarkable  manner,  and  that  from  all  portions  of  the 
lower -lying  parts  of  the  island  situated  to  the  north  of  the  Peak  of  Rakata,  that  is 
from  the  area  within  the  walls  of  the  original  crater,  outbursts  were  going  on. 
This  account  of  the  state  of  the  volcano  on  August  the  11th  is  very  interesting 
indeed,  oa  being  the  last  which  we  have  before  the  great  paroxysm  which  occurred 
towards  the  end  of  the  same  month. 

The  vessels  which  passed  close  to  Krakatoa  between  the  11th  of  August  and  the 
time  of  the  great  catastrophe  reported  a  heavy  rain  of  pumice  and  dust  and  constant 
loud  explosions  as  taking  place.  On  the  25th  the  dust  had  been  carried  to  such  a 
height  as  to  begin  to  fall  at  Telok  Betong,  nearly  fifty  miles  distant. 

The  eruption  which  began  on  May  the  20th,  and  culminated  in  the  tremendous 
explosion  of  August  the  27th,  thus  appears  to  have  exhibited  the  following  vicissi- 
tudes : — Bursting  out  with  somewhat  sudden  violence,  the  eruption  from  Perboewatan 
seems  to  have  had  sufficient  force  to  carry  the  volcanic  dust  to  various  points  along  the 
shores  of  Java  and  Sumat  ra.  After  this  sudden  outburst,  there  was  a  rapid  and  marked 
decline  in  violence,  and  then  a  gradual  increase  till  June  the  24th,  when  a  second 
crater  had  opened  in  the  centre  of  the  island.  The  eruptive  force  still  increasing,  a 
third  crater  made  its  appearance^  and  innumerable  smaller  vents  were  originated  all 
over  the  surface  of  the  fiUed-up  crater  of  the  great  volcano.  From  this  time  the 
activity  seemed  still  constantly  to  increase,  till  its  grand  culmination  on  the  27th  of 
August. 

The  Eruption  of  August  2(jth  and  27th,  1883. 

On  the  afternoon  of  the  26th  of  August,  and  through  the  succeeding  night  and 
day  till  the  early  morning  of  the  28th  of  August,  it  was  evident  that  the  long- 
continued  moderate  eruptions  (Strombolian  stage)  which  had  for  some  days  been 
growing  in  intensity,  had  passed  into  the  paroxysmal  (Vesuvian)  staga  In  order  to 
weigh  the  evidence  which  we  have  concerning  the  nature  of  this  critical  and  most 
interesting  period  of  the  eruption  of  Krakatoa,  it  may  be  well  to  consider  what  were 
the  facilities  for  observation  possessed  by  the  several  individuals  from  whom  the 
reports  concerning  the  eruptions  were  obtained. 

Situated  respectively  at  a  distance  of  94  and  100  English  miles  to  the  east  of 
Krakatoa  are  the  two  important  towns  of  Batavia  and  Buitenzorg.  In  both  these 
places,  numerous  Europeans  capable  of  making  accurate  observations  were  resident ; 
there  were  also  self-recording  instruments,  the  tracings  of  which  have  proved  of  the 
greatest  value  in  these  enquiries.  At  numerous  small  towns  and  villages  along  the 
Javan  and  Sumatran  coasts  of  the  Strait  of  Sunda,  and  in  the  five  lighthouses,  two  of 
which  were  destroyed,  European  officials  were  located.  Many  of  these  fled  during  the 
terrible  night  of  the  26th  of  August,  and  others  were  drowned  by  thei  great  sea- 
waves  which  submerged  all  the   coast-towns  on  the  morning   of  the  27th.     Very 


PROP.  JUDD  ON  THE  VOLCANIC  PHENOMENA.  15 

admirably  has  Mr.  Yerbeek  collected  and  discussed  the  reports  made  by  the  officials 
of  the  coast- towns  and  villages  who  survived  that  night  of  horrors. 

Perhaps,  however,  the  most  important  evidence  of  what  was  actually  going  on  at 
Krakatoa  during  the  crisis  of  the  eruption  is  that  derived  from  witnesses  on  board 
ships  which  sailed  between  Java  and  Sumatra  while  the  great  outburst  was  in 
progress,  or  those  that  were  at  the  time  in  the  immediate  vicinity  of  either  the 
eastern  or  western  entrance  of  the  Sunda  Strait.  From  many  more  distant  points, 
however,  valuable  confirmatory  or  supplementary  evidence  has  been  obtained,  for 
which  we  are  indebted  to  the  captains  or  passengers  of  vessels  passing  through  the 
eastern  seas  during  that  period. 

Only  three  European  ships  appear  to  have  been  actually  within  the  Sunda 
Strait  during  the  height  of  the  eruption  on  the  night  of  the  26th  of  August  and  the 
early  morning  of  the  27th,  and  to  have  escaped  destruction,  so  that  those  on  board 
could  tell  the  tale  of  what  they  witnessed. 

The  greatest  opportunities  for  observation  seem  to  have  been  those  which  were 
afforded  to  Captain  Watson  of  the  British  ship  Charles  Bed,  then  on  its  voyage  to 
Hong  Kong.  This  vessel  passed  Princes  Island  at  9  a.m,  on  Sunday  the  26th  of 
August;  at  noon  she  was  on  the  south-west  side  of  Krakatoa ;  and  at  4.15  p.m.  she 
reached  a  point  nearly  due  south  of  the  volcano,  and  about  10  miles  distant  from  it. 
The  darkness  being  too  great  to  permit  of  safe  navigation,  sail  was  shortened,  and 
through  the  whole  night  the  vessel  was  kept  beating  about  on  the  east  of  the  volcano, 
and  within  a  dozen  miles  from  it.  At  6  a.m,  on  the  27th,  the  Java  shore  was  sighted, 
and  the  vessel  was  enabled  to  continue  her  voyage. 

The  Batavian  steamship  Oouvemeur-GeneracU  Loudon,  Commandant  T.  H. 
liiNDEHAN,  left  Batavia  on  the  morning  of  the  26th  of  August,  and  reached  Anjer  at 
2  p.m.  the  same  day.  Leaving  that  port  at  2.45  p.m.,  she  sailed  for  Telok  Betong, 
taking  a  number  of  coolies  and  women  as  passengers,  and  passing  about  80  miles 
north  of  Krakatoa,  reached  her  destination  at  7.30  p.m.  Finding  at  midnight 
that  it  was  impossible,  on  account  of  the  storm  which  was  raging,  to  communicate  with 
the  shore,  the  vessel  steamed  out  into  the  bay  and  anchored.  She  thus  escaped  being 
stranded  by  the  great  sea-waves  of  the  early  morning,  like  the  unfortunate  Govern- 
ment steamer  Berouw,  which  was  at  this  time  anchored  close  to  the  pier-head  at 
Telok  Betong.  At  7  30  a.m.  on  the  27th,  the  steamer  G.  G.  Loudon  started  to  return 
to  Anjer,  but  had  to  come  to  anchor  at  10  o'clock  on  account  of  the  rain  of  pumice, 
and  the  storm  that  was  raging.  During  Tuesday,  the  28th,  she  steamed  round  the 
west  and  south  sides  of  Krakatoa,  called  at  the  part  of  the  coast  where  Anjer  formerly 
stood,  and  then  proceeded  to  Batavia. 

The  Dutch  barque  Marie,  engaged  in  the  salt- trade,  was,  during  the  whole  time  of 
the  eruption,  anchored  off  Telok  Betong.  On  the  morning  of  the  27th  of  August,  thanks 
to  the  precaution  of  putting  out  a  third  anchor,  she  rode  safely,  and  was  able  to  avoid 
being  stranded  by  the  gigantic  sea- waves,  which  swept  on  to  the  land  the  Government 


16  PROF.  JUDD  ON  THE  VOLCANIC  PHENOMENA. 

steamer  Berouw,  three  schooners,  and  many  smaller  craft  lying  off  the  same  port. 
The  vessel  appears  to  have  been  at  times  in  imminent  danger,  but  only  four  of  the 
persons  on  board  of  her  were  drowned. 

During  the  whole  of  Sunday,  the  26th  of  August,  two  vessels,  the  barque 
Norham  Castle,  Captain  O.  Sampson,  and  the  ship  Sir  Robert  Sale,  Captain  W.  T. 
WooLDRiDGE,  were  at  the  eastern  entrance  of  the  Strait,  and  about  40  miles  from 
Krakatoa.  On  the  morning  of  Monday,  the  27th,  both  these  vessels  entered 
the  Strait,  but  owing  to  the  darkness,  neither  made  much  progress  till  the  morning 
of  the  28th,  when,  falling  in  with  each  other,  they  made  their  way  in  company, 
but  with  much  difl&culty,  through  the  Strait. 

The  Dutch  hopper-barge,  Tegal,  which  sailed  from  Batavia  for  Merak  early  on 
Monday,  the  27  th  of  August,  remained  at  anchor  near  the  eastern  entrance  of  the 
Strait  during  the  great  darkness,  but  on  Tuesday,  the  28th,  entered  the  Strait 

On  the  morning  of  Sunday,  the  26th  of  August,  the  ship  Berhice,  of  Greenock, 
Captain  William  Logan,  was  at  the  western  entrance  of  Sunda  Strait,  and  about 
40  miles  from  Krakatoa.  This  vessel  remained  beating  about  the  entrance  till 
Wednesday,  the  29th,  when  she  was  able  to  sail  through  the  Strait. 

These  are  the  vessels  which,  during  the  crisis  of  the  great  eruption,  were  in  the 
most  favourable  positions  for  those  on  board  of  them  to  make  observations  concerning 
what  was  taking  place  at  Krakatoa.  The  approximate  positions  of  these  vessels  are 
shown  in  the  accompanying  chart  (Fig.  9).  Let  us  now  turn  our  attention  to  some 
other  vessels  which  were  at  greater  distances  from  the  scene  of  eruption,  but,  from 
the  captains  or  passengers  on  board  which,  valuable  information  has  been  received. 

The  Norwegian  barque  Borjild,  Captain  Amundsen,  was  at  anchor  near  Great 
Kombuis  Island,  75  miles  east-by-north  of  Krakatoa,  during  the  26th  and  27th  of 
August. 

The  British  ship  Medea,  Captain  Thomson,  was,  at  2  p.m.  on  the  26th,  in  the 
vicinity  of  the  last-mentioned  vessel,  and  sailing  eastward  came  to  anchor  about  89 
miles  from  Krakatoa. 

The  American  barque  William  H.  Besse,  Captain  Baker,  on  its  way  from 
Manilla  to  Boston,  U.S.A.,  having  called  at  Batavia,  was  in  the  same  neighbourhood, 
and  on  Wednesday,  29th,  and  Thursday,  30th  of  August,  was  passing  through  the 
Strait. 

The  British  steamer  Anerley,  Captain  Strachan,  bound  from  Singapore  to 
Mauritius,  was,  on  the  26th  of  August,  in  Banca  Strait,  250  English  miles  north  of 
Krakatoa.  During  the  27th  the  steamer  remained  at  anchor  near  North  Watcher 
Island,  92  English  miles  north-east  of  the  volcano. 

The  Siamese  barque  Thoon  Kramoom,  Captain  Andersen,  bound  from  Bankok  to 
Falmouth,  lay,  on  the  27th  and  28th  of  August,  in  the  Strait  of  Banca,  230  English 
miles  north  of  Krakatoa,  and,  sailing  southwards,  passed  through  the  Strait  of  Sunda 
on  the  31st  of  August. 


PROF.  JUDD  ON  THE  VOLCANIC  PHENOMENA. 


17 


18  PROF.  JUDD  ON  THE  VOLCANIC  PHENOMENA. 

Several  vessels,  among  which  was  the  barque  Hope,  were  lying  in  Batavia  Bay 
during  the  great  paroxysmal  outburst. 

The  mail  steamer  Frinses  Wilhelmina,  which  passed  through  the  Strait  on  the 
23rd  of  August,  coming  from  the  west,  remained  at  anchor  at  Batavia  during  the 
time  of  the  great  eruption. 

Among  vessels  which  were  at  still  greater  distances  from  the  volcano  during  the 
time  of  the  great  outburst,  the  following  may  be  mentioned  as  those  from  which 
information  and  specimens  of  the  falling  pmnice  and  duet  have  been  received  : — 

The  British  ship  Bay  of  Naples,  Captain  TroiiARSH,  was,  during  the  eruption, 
about  138  English  miles  south  of  Java's  First  Point,  and  the  barque  Luda  was 
about  300  miles  to  the  south-east  of  Krakatoa. 

From  the  seas  to  the  west  of  the  Strait  of  Sunda  we  have  information  from  the 
steamship  SimUiy  Captain  M.  Nicholson,  where  dust,  falling  at  a  distance  of  about 
1,150  English  miles  from  the  volcano,  was  collected,  and  from  the  barque  Jonc^ 
Captain  L.  Reid,  at  about  600  English  miles  from  the  Strait.  On  board  the  British 
ships  Earl  of  Beaconsjield,  and  the  Ardgotvan,  Captain  Isbisteb,  and  the  German 
brig  Catheriney  dust  fell  when  they  were  between  900  and  1,100  English  miles 
from  Krakatoa  ;  and  on  board  the  British  barque  Arabella,  Captain  Williams,  when 
about  1,100  English  miles  from  Krakatoa. 

The  mail  steamer  Frins  Frederik,  on  its  way  to  Holland,  passed  near  Krakatoa 
on  the  25th  of  August,  and  the  steamer  Batavia  sailed  from  Padang  to  Vlakke 
Hoek  on  the  evening  of  the  27th. 

The  Frins  Hendrik,  a  Dutch  man-of-war,  was  ordered  to  the  Strait  of  Sunda 
immediately  after  the  eruption,  in  order  to  succour  the  survivors. 

H.M.S.  Magpie,  Commander  the  Hon.  F.  C.  P.  Vereker,  was  at  Sandakang, 
N.  Borneo,  at  the  time  of  the  eruption,  and  on  the  18  th  of  October  visited  the  Strait 
for  the  purpose  of  examining  the  changes  which  had  taken  place.  Somewhat  later 
H.M.S.  Merlin,  Commander  R.  C.  Brunton,  visited  the  locality,  and  sent  in  a  report 
to  the  Admiralty. 

From  various  ports,  accounts  have  been  received,  sent  by  British  Consuls  and 
by  residents,  and  many  of  these  have  proved  to  be  of  great  service  to  the  Krakatoa 
Committee. 

The  log-books  of  the  different  vessels  mentioned,  and  narratives  written  by  the 
captains  and  passengers  on  board  of  them,  taken  in  conjunction  with  the  reports 
collected  with  so  much  care  by  Mr.  Vgirbeek,  have  afforded  the  means  of  compiling 
the  following  account  of  what  occurred  at  Krakatoa  during  Sunday,  the  26th,  and 
Monday,  the  27th,  August. 

The  vessels  passing  through  the  Strait,  as  well  as  the  observers  on  land,  all 
reported  a  very  marked  though  gradual  increase  in  the  violence  of  the  eruption 
during  the  three  days  which  preceded  Sunday,  the  26th  of  August. 


PROF.   JUDD   ON   THE  VOLCANIC   PHENOMENA.  19 

On  that  day,  about  1  p.m.,  the  detonations  caused  by  the  explosive  action 
attained  such  violence  as  to  be  heard  at  Batavia  and  Buitenzorg,  about  100  English 
miles  away. 

At  2  p.m.  Captain  Thomson,  of  the  Medea,  then  sailing  at  a  poiut  76  English 
miles  E.N.E.  of  Krakatoa,  saw  *'  a  black  mass  rising  up  like  a  smoke,  in  clouds,"  to  an 
altitude  which  has  been  estimated  as  being  no  less  than  17  miles.  If  this  estimate  be 
correct,  some  idea  of  the  violence  of  the  outburst  can  be  formed  from  the  fact  that 
during  the  eruption  of  Vesuvius  in  1872  the  column  of  steam  and  dust  was  pro- 
pelled to  the  height  of  from  only  4  to  5  miles. 

The  great  detonations  at  this  time  were  said  to  be  taking  place  at  intervals  of 
about  ten  minutes. 

By  3  p.m.  the  sounds  produced  by  the  explosions  at  Krakatoa  had  so  far  increased 
in  loudness  that  they  were  heard  at  Bandong  and  other  places  150  miles  away;  and  at 
5  p.m.  they  had  become  so  tremendous  that  they  were  heard  all  over  the  island  of 
Java,  and  at  many  other  equally  distant  localities.  At  Batavia  and  Buitenzorg  they 
were,  during  the  whole  night,  so  violent  that  few  people  in  the  district  were  able 
to  sleep ;  the  noise  is  described  as  being  like  the  discharge  of  artillery  close  at 
hand,  and  as  causing  rattling  of  the  windows  and  shaking  of  pictures,  chandeliers, 
and  other  hanging  bodies.  Nearly  all  observers  agree  that  there  was  nothing  in  the 
nature  of  earthquake-shocks,  but  only  strong  air-vibrations. 

Captain  Watson,  of  the  Charles  Bal,  who  was  only  10  miles  south  of  the 
volcano  during  this  Sunday  afternoon,  describes  the  island  as  being  covered  with  a 
dense  black  cloud ;"  clouds  or  something  were  being  propelled  from  the  north-east 
point  with  great  velocity ; "  sounds  like  discharges  of  artillery  at  intervals  of  a  second 
of  time,  and  a  crackling  noise,  probably  due  to  the  impact  of  fragments  in  the 
atmosphere,  were  heard ;  the  whole  commotion  increasing  towards  5  p.m.,  when  it 
became  so  intense  that  the  Captain  feared  to  continue  his  voyage,  and  began  to 
shorten  sail.  From  5  to  6  p.m.  a  rain  of  pumice  in  large  pieces,  quite  warm,  fell  upon 
the  ship. 

Captain  Wooldridgk,  of  the  Sir  R.  Sale,  viewing  the  volcano  from  the  north- 
east at  sunset  on  Sunday  evening,  the  26th,  describes  the  sky  as  presenting  "a  most 
terrible  appearance,  the  dense  mass  of  clouds  being  covered  with  a  murky  tinge, 
with  fierce  flashes  of  lightning.''  At  7  p.m.,  when  the  dense  vapour  and  dust-clouds 
rendered  it  intensely  dark,  the  whole  scene  was  lighted  up  from  time  to  time  by  the 
electrical  discharges,  and  at  one  time  the  cloud  above  the  mountain  presented  "  the 
appearance  of  an  immense  pine-tree,  with  the  stem  and  branches  formed  with  volcanic 
lightning."  The  air  was  loaded  with  excessively  fine  ashes,  and  there  was  a  strong 
sulphurous  smell.  Captain  O.  Sampson,  of  the  Norham  Castle,  who  was  in  the  same 
neighbourhood,  gives  a  similar  account  of  what  he  witnessed.  The  steamer 
G.    G.    Loudon   passed    to    the    north-west    and    west    of   the   volcano,   within    a 

distance  of  20  or  30  miles ;  it  was  seen  to  be  "  casting  forth   enormous  columns 

d2 


20  PROF.  JUDD   ON   THE  VOLCANIC  PHENOMENA. 

of   smoke,"  and    the  vessel    passed    through   "a  rain   of   ashes    and    small    bits 
of  stone." 

During  the  night,  while  the  Charles  Bed  remained  beating  about  on  the  east  of 
Krakatoa,  and  within  about  a  dozen  miles  of  the  island,  Captain  Watson  records 
the  phenomena  of  **  chains  of  fire,  appearing  to  ascend  "  between  the  volcano  and  the 
sky,  while  on  the  south-west  side  there  seemed  to  be  "  a  continual  roll  of  balls  of 
white  fire."  These  appearances  were  doubtless  caused  by  the  discharge  of  white- 
hot  fragments  of  lava,  and  their  roll  down  the  sides  of  the  peak  of  Kakata,  which 
was  still  standing. 

The  air  at  this  distance,  though  the  wind  was  strong  at  the  time,  was  described 
by  Captain  Watson  as  being  "hot  and  choking,  sulphurous,  with  a  smell  as  of 
burning  cinders ; "  masses  like  "  iron-cinders  "  fell  on  the  ship,  and  the  lead  firom  a 
bottom  of  30  fathoms  came  up  quite  warm.  From  midnight  till  4  a.m.  explosions 
continually  took  place,  "  the  sky,  one  second  intense  blackness,  the  next  a  blaze  of 
fire." 

All  these  details  prove  conclusively  that  Krakatoa  had  arrived  at  the  paroxysmal 
phase  of  eruption.  The  explosive  bursts  of  vapour  beginning  on  the  afternoon  of 
Sunday  and  continuing  at  intervals  of  ten  minutes,  increased  in  violence  and  rapidity, 
and  from  sunset  till  midnight  there  was  an  almost  continuous  roar,  which  moderated 
a  little  towards  early  morning.  Each  explosive  outburst  of  steam  would  have  the 
effect  of  removing  the  accumulating  pumice  from  the  surface  of  the  melted  lava,  by 
blowing  it  into  the  atmosphere,  and  the  cauldron  of  white-hot  lava  would  then  have 
its  glowing  surface  reflected  in  the  clouds  of  vapour  and  dust  hanging  above. 

The  numerous  vents  on  the  low-lying  parts  of  Krakatoa,  which  were  recorded  as 
having  been  seen  by  Captain  Ferzenaar  on  the  11th  of  August,  had,  doubtless,  by 
this  time  become  more  or  less  united,  and  the  original  crater  of  the  old  volcano  was 
being  rapidly  emptied  by  the  great  paroxysmal  explosions  which  commenced  in  the 
afternoon  of  the  26th  of  August. 

All  the  eye-witnesses  are  in  agreement  as  to  the  splendour  of  the  electrical 
phenomena  displayed  during  this  paroxysmal  outburst.  Captain  Wooldridge,  viewing 
the  eruption  in  the  afternoon  from  a  distance  of  40  miles,  speaks  of  the  great 
vapour-cloud  looking  like  **an  immense  wall  with  bursts  of  forked  lightning  at  times 
like  large  serpents  rushing  through  the  air,"  After  sunset  this  dark  wall  resembled 
a  **  blood-red  curtain,  with  the  edges  of  all  shades  of  yellow ;  the  whole  of  a  murky 
tinge,  with  fierce  flashes  of  lightning."  Captain  O.  Sampson,  viewing  the  volcano 
from  a  similar  position  at  the  same  time,  states  that  Krakatoa  "  appeared  to  be  alight 
with  flickering  flamea  rising  behind  a  dense  black  cloud ;  at  the  same  time  balls  of 
fire  rested  on  the  mastheads  and  extremities  of  the  yard-arms." 

Captain  Watson  states  that  during  the  night  the  mastheads  and  yard-arms  of  his 
ship  were  *'  studded  with  corposants,''  and  records  the  occurrence  of  "a  peculiar  pinky 
flame  coming  from  clouds  which  seemed  to  touch  the  mastheads  and  yard-arms."  From 


PROP.   JUDD  ON  THE  VOLCANIC   PHENOMENA.  21 

the  G.  G.  Loudon,  lying  in  the  Bay  of  Lampong,  40  or  50  English  miles  north-west 
of  the  volcano,  it  was  recorded  that  "  the  lightning  struck  the  mainmast-conductor 
five  or  six  times,"  and  that  **  the  mud-rain  which  covered  the  masts,  rising,  and 
decks,  was  phosphorescent,  and  on  the  rigging  presented  the  appearance  of  St.  Elmo's 
fire.  The  natives  engaged  themselves  busily  in  putting  this  phosphorescent  light  out 
with  their  hands,  and  were  so  intent  on  this  occupation  that  the  stokers  left  the 
engine-rooms  for  the  purpose,  so  that  the  European  engineers  were  left  to  drive  the 
machinery  for  themselves.  The  natives  pleaded  that  if  this  phosphorescent  light,  or 
any  portion  of  it,  found  its  way  below,  a  hole  would  burst  in  the  ship  ;  not  that  they 
feared  the  ship  taking  fire,  but  they  thought  the  light  was  the  work  of  evil  spirits, 
and  that  if  the  ill-omened  light  found  its  way  below,  the  evil  spirits  would  triumph 
in  their  design  to  scuttle  the  ship." 

This  abundant  generation  of  atmospheric  electricity  is  a  familiar  phenomenon  in 
all  volcanic  eruptions  on  a  grand  scale.  The  steam-jets  rushing  through  the  orifices 
of  the  earth's  crust  constitute  an  enormous  hydro-electric  engine ;  and  the  firiction  of 
ejected  materials  striking  against  one  another  in  their  ascent  and  descent  also  does 
much  in  the  way  of  generating  electricity. 

Up  to  late  in  the  afternoon  of  the  26th  of  August,  the  phenomena  exhibited  by 
Krakatoa  were  precisely  similar  to  those  witnessed  at  every  great  paroxysmal  volcanic 
eruption.  But  at  that  time  the  effects  of  the  somewhat  peculiar  position  of  the 
Krakatoa  crater  began  to  be  apparent.  Lying  as  it  does  so  close  to  the  sea-level,  the 
work  of  evisceration  by  explosive  action  could  not  go  far  without  the  waters  of  the 
ocean  finding  their  way  into  the  heated  mass  of  lava  from  which  the  eruption  was 
taking  place. 

It  is  often  assumed  that  if  a  mass  of  water  come  into  contact  with  molten  lava 
a  terrible  outburst  of  steam,  producing  a  great  volcanic  eruption,  must  be  the  conse- 
quence, and  some  vulcanologists  insist  that  the  admission  of  water  by  fissures  into 
subterranean  reservoirs  of  lava  is  the  determining  cause  of  all  volcanic  outbreaks. 
But  careful  observation  does  not  give  much  countenance  to  this  view.  Lava-streams 
have  frequently  been  seen  to  flow  into  the  sea,  and  although  a  considerable  generation 
of  steam  occurred  when  the  molten  mass  first  came  in  contact  with  the  water,  yet 
none  of  the  prolonged  effects  which  are  popularly  supposed  to  result  from  the 
conflict  of  fire  and  water  were  found  to  occur.  The  surface  of  the  lava-current 
becoming  rapidly  chilled,  a  layer  of  slowly  conducting  rock  is  formed  at  its  surface, 
and  then  the  gradual  cooling  down  of  the  whole  mass  ensues,  without  further 
disturbance. 

By  the  lowering  of  the  mass  lying  within  the  old  crater-ring  of  Krakatoa,  and 
the  diminution  in  height  of  the  crater- walls,  water  would  from  time  to  time  find  a 
way  to  the  molten  lava  below ;  each  such  influx  of  water  would  no  doubt  lead  to  the 
generation  of  some  steam  with  explosive  violence,  and  the  production  of  small  sea-waves 
which  would  travel  outwards  from  Krakatoa  as  a  centre.     From  the  reports  made  by 


22  PROF.  JUDD  ON  THE  VOLCANIC   PHENOMENA. 

the  oflScials  at  Anjer  and  other  places  on  the  shores  of  Java  and  Sumatra,  the  produc- 
tion of  such  waves,  which  were  only  a  few  feet  in  height,  began  to  be  observed  about 
5,30  p.m.  on  Sunday,  the  26th  of  August,  and  continued  at  irregular  intervals  all 
through  the  night.  Towards  morning,  however,  the  chilling  effects  of  the  water  which 
had  from  time  to  time  found  its  way  to  the  molten  materials  below  the  volcano 
began  to  be  felt,  and  as  a  result  a  diminution  in  the  activity  of  the  volcano  is  recorded. 

If,  as  I  shall  show  when  I  proceed  to  discuss  the  nature  of  the  materials  ejected 
from  Krakatoa,  the  cause  of  the  eruptive  action  was  due  to  the  disengagement  of 
volatile  substances  actually  contained  in  those  matenals,  the  checking  of  the  activity, 
by  the  influx  into  the  molten  mass  of  vast  quantities  of  cold  sea  water,  would  have 
the  same  efiect  as  fastening  down  the  safety-valve  of  a  steam-boiler,  while  the  fires 
below  were  maintained  in  full  activity. 

The  constant  augmentation  of  tension  beneath  Krakatoa,  in  the  end  gave  rise  to 
a  series  of  tremendous  explosions,  on  a  far  grander  scale  than  those  resulting  directly 
from  the  influx  of  the  sea-water  into  the  vent ;  the  four  principal  of  these  occurred, 
according  to  the  careful  investigations  of  Mr.  Verbeek,  at  5.30,  6.44,  10.2,*  and 
10.52,  Krakatoa  time,  on  the  morning  of  August  the  27th.  Of  these,  the  third, 
occurring  shortly  after  10  o'clock,  was  by  far  the  most  violent,  and  was  productive 
of  the  most  wide-spread  results. 

Although  no  one  was  near  enough  to  Krakatoa  during  these  paroxysmal  out- 
bursts to  witness  what  took  place  there,  a  comparison  of  the  condition  of  the  volcano 
and  of  the  surrounding  seas  before  and  after  these  terrible  manifestations  of  the 
subterranean  forces,  leaves  little  doubt  as  to  the  real  nature  of  the  action. 

In  the  first  place,  we  find  that  the  whole  of  the  northern  and  lower  portion  of  the 
Island  of  Krakatoa  disappeared,  with  the  exception  of  a  bank  of  pumice  and  one  small 
isolated  rock,  about  ]  0  yards  square,  which  was  left  sttinding  above  the  ocean  with  deep 
water  all  round  it.  This  rock  consists  of  solid  pitchstone,  and  probably  represents  a 
dyke  or  plug  filling  the  throat  of  one  of  the  volcanic  cones  that  formerly  occupied 
the  old  crater.  At  the  same  time  a  large  portion  of  the  northern  part  of  the  basaltic 
cone  of  Kakata  was  destroyed  and  a  nearly  vertical  cliff  formed,  giving  rise  to  a 
magnificent  section  which  afforded  a  perfect  insight  into  the  internal  structure  of  the 
volcano.  {See  Plate  11. ,  Fig.  2.)  The  depth  of  the  great  crateral  hollow  which  was 
produced,  where  the  northern  part  of  Krakatoa  formerly  rose  to  heights  of  from  300 
to  1,400  feet  above  the  sea  level,  in  some  places  exceeds  1,000  feet  below  that  same 
level.     {See  Fig.  10,  p.  23.) 

In  attempting  to  judge  of  the  effects  produced  around  the  flanks  of  the  great 
crater  of  Krakatoa,  we  have  the  two  new  and  very  detailed  charts  prepared  by  the 
Royal  Dutch  surveying  vessel  Hyclrograaf,  under  Commandant  C.  van  Doorn. 
The  first  of  these  was  the  result  of  a  careful  survey  made  immediately  after  the 

*  GorrespondiDg  to  the  wave  mentioned  on  p.  69  as  9  b.  58  m.  Krakatoa  time  =  2  h.  56  m.  G.M.T. 


PEOF.  JUDD  ON  THE  VOLCANIC  PHENOMENA.  28 

eruption,  and  was  published  on  October  the  26th,  1883,  while  the  second  appeared 
somewhat  later,  after  the  new  Islands  of  Steers  and  Calmeyer  had  been  reduced  to 


Pig.  10. — Outline  of  the  crater  of  Krakatoa  as  it  is  at  the  present  time.  The  dotted  line  indicates  the 
portions  blown  away  in  the  paroxysmal  outburst  of  August,  1883,  and  the  changes  in  form  of 
the  flanks  of  the  mountain  by  the  fall  of  ejected  materials  upon  them, 

sandbanks.  These  are  reproduced  as  Plates  XXXII.  and  XXXIII.  following  Part 
III. ;  but  it  is  a  very  unfortunate  circumstance  that  the  old  charts  of  the  Strait  of 
Sunda  are  far  from  accurate,  and  thus  considerable  difficulty  arises  when  we  attempt 
to  make  an  exact  estimate  of  the  changes  produced  by  the  eruption.  {See  Fig.  1 1,  p.  24.) 

Certain  it  is  that  the  portion  of  the  Island  of  Krakatoa  which  disappeared 
during  the  eruption  was  equal  to  about  two-thirds  of  the  original  area,  the  part  that 
remained  consisting  only  of  the  southern  moiety  of  the  volcanic  cone  of  Rakata. 
Of  this  fragment  the  southern  outline,  according  to  the  new  charts,  differs  considerably 
from  that  of  the  southern  shore  of  the  original  island,  and  its  height,  if  the  old 
charts  can  be  depended  upon,  was  increased  from  2,623*  to  2,750  feet.  But  the  top 
and  sides  of  this  fragment  of  the  cone  of  Rakata  are  so  covered  by  masses  of  ejected 
materials  that  the  alteration  in  its  form  and  height  are,  it  appears  to  me,  sufficiently 
accounted  for  without  requiring  us  to  call  in  any  theory  of  general  upheaval  of  the  mass. 

Of  the  other  islands  of  the  group,  Poolsche  Hoedje  (Polish  Hat)  has  entirely 
disappeared;  Lang  Island  has  been  increased  by  an  addition  to  its  northern  extremity, 
and  its  height  above  the  sea  seems  to  have  been  augmented,  the  whole  of  the 
vegetation  that  formerly  covered  it  being  deeply  buried  by  ejected  matters;  and 
lastly,  Verlaten  Island  has,  by  accretions  on  the  side  farthest  away  from  the  central 
crater,  been  enlarged  to  more  than  three  times  its  former  area,  while  a  considerable 
addition  has  been  made  to  its  height. 

In  judging  of  the  alterations  in  the  form  of  the  sea-bottom  around  the  Krakatoa 
group,  we  have  to  rely  upon  the  few  and  not  very  accurate  soundings  in  the  old 
chart  of  the  Strait.  From  a  comparison  of  these  with  the  depths  given  in  the  new 
chart,  we  can  scarcely  doubt  that  over  a  circle  with  a  radius  of  10  or  12  miles  from 
the  centre  of  the  Krakatoa  volcano,  the  sea-bottom  outside  the  great  crater  has  been 
raised  by  an  amount  which  varies  from  10  to  60  feet.  Mr.  Verbeek  concluded 
however,  that  along  a  line  8  or  9  miles  in  length,  and  extending  westward  from  the 
great  crater,  an  increase  of  depth  has  taken  place,  and  this  is  not  improbably  due  to 
the  opening  of  a  fissure  on  the  flanks  of  the  submerged  cone. 

•  According  to  Verbeek,  the  height  previous  to  the  eruption  was  2,697  feet.     After  the  eruption  he 
sajs  the  height  was  2,730  feet,  but  was  reduced  by  June,  1886,  to  2,677  feet. 


24 


PROF.  JUDD  ON  THE  VOLCANIC  PHENOMENA. 


In  the  so-called  New  or  Sebesi  Channel,  between  Krakatoa  and  Sebesi  Islands, 
the  original  depth  of  water  was  much  less  than  on  the  other  sides  of  the  Krakatoa 


Sea  Rwk^>  \^.j^ 


Be*»Rlc 


r^^^ 


SEBESI  I. 


|:-- •••••-•'?T««T*       »«~~«~»,,;,^^^^^    ^JkfM$Un  RmL 


^^"^ 


SEBESI    CHANNEL    '*''""' 


r 


^ 


LANG  I. 


^vTST- 


CALUSTER 


KRAK/VTOA  I. 


^^SiKlHliKfAli'i'''-''' 


L^ 


OREAT    CHANNEL 


Enftlitli  Miles. 


■jy^yft' 


Fio.  11. — Map  of  Krakatoa  and  the  surrounding  ulandsj  from  the  Chart  prepared  immediately  after  the 
Eruption,  Later  charts  show  the  islands  of  Steers  and  Galmeyer  reduced  to  sandbanks.  The  shaded 
areas  show  the  form  of  the  islands  a^ccording  to  the  old  chart.  Much  of  the  discrepancy  between 
the  southern  limit  of  Krakatoa  in  the  two  maps  is  due  to  the  imperfection  of  the  old  survey. 
Dotted  lines  show  sand-hanks  and  lines  of  breakers, 

group,  seldom,  indeed,  exceeding  20  fathoms ;  and  several  rocks  in  this  channel  rose 
above  the  sea-level.  After  the  eruption  it  was  found  that  this  channel  was  com- 
pletely blocked  by  banks  composed  of  volcanic  materials,  and  two  portions  of  these 
banks  rose  above  the  sea  as  islands,  which  received  the  name  of  Steers  Island  and 


PROF.  JUDD  ON  THE  VOLCANIC  PHENOMENA.  25 

Calmeyer  Island  By  the  action  of  the  waves,  however,  these  islands  were,  in  the 
course  of  a  few  months,  completely  washed  away,  and  their  materials  distributed  over 
the  sea  bottom. 

The  changes  which  took  place  in  the  forms  of  the  islands  and  in  the  depth  of 
the  sea  around  them,  have  been  supposed  by  some  to  indicate  a  general  elevation  of 
the  islands  of  the  Krakatoa  group,  accompanied  by  a  great  subsidence  of  the  central  or 
crateral  area.  A  careful  study  of  these  changes  in  the  light  of  what  is  known  to  have 
taken  place  at  other  volcanic  centres  leads  me  to  adopt  a  wholly  different  conclusion. 

The  action  going  on  within  a  volcanic  vent  during  eruption  is  in  all  essential 
features  identical  with  that  which  takes  place  in  the  throat  of  a  geyser.  In  both 
cases  we  have  a  mass  of  heated  liquid,  in  the  midst  of  which  large  quantities  of 
gaseous  materials  are  being  disengaged  so  as  to  escape  into  the  atmosphere  as  the 
pressure  is  relieved,  and  these  escaping  gases  carry  up  with  them  portions  of  the 
liquid  in  which  they  have  been  confined.  Now  just  as  the  throwing  of  sods  and 
earth  into  the  tube  of  a  geyser,  by  causing  a  check  in  the  escape  of  steam  and  water 
and  thereby  leading  to  an  augmentation  of  the  tension  of  the  elastic  fluids  below, 
gives  rise  to  a  more  than  usually  violent  explosion,  so  the  interruption  to  the  regular 
ejections  going  on  at  Krakatoa,  consequent  on  the  chilling  of  the  surface  of  the  lava 
in  the  vent  by  inrushes  of  sea-water,  caused  a  check  and  then  a  rally  of  the  pent-up 
force  of  gases  seeking  to  escape  from  the  molten  mass.  The  serious  catastrophic 
outbursts  that  produced  such  startling  effects  both  in  the  air  and  in  the  ocean 
appear  to  me  to  have  been  the  direct  consequences  of  this  "  check  and  rally  "  of  the 
subterranean  forces. 

In  these  last  terrible  outbursts,  in  which  the  volcano  rapidly  expended  its 
remaining  force,  we  are  evidently  dealing  with  the  breaking  up  and  ejection  of  solid 
lava  constituting  the  framework  of  the  volcano,  and  not  with  the  simple  dissipation  of 
the  lava-froth  (pumice)  as  during  all  the  earlier  stages  of  the  eruption.  That  the 
materials  were  not  carried  far  from  the  centre  of  ejection  is  shown  by  the  fact  that 
no  falls  of  coarse  materials  are  recorded  from  any  of  the  vessels  that  were  within  or 
near  the  Strait  at  the  time,  but  the  bulk  of  the  solid  fragments  thrown  out  during  these 
great  explosions  must  have  fallen  back  into  the  sea,  upon  and  immediately  around  the 
flanks  of  the  volcano  itiself.  This  is  proved  by  the  alteration  in  the  forms  of  the 
islands  of  the  Krakatoa  group,  and  by  the  change  in  the  height  of  the  floor  of 
the  surrounding  ocean.  By  these  grand  explosive  outbursts  the  old  crater  was 
completely  eviscerated,  and  a  cavity  formed,  more  than  1,000  feet  in  depth,  whUe 
the  solid  materials  thrown  out  froln  the  crater  were  spread  over  the  flanks  of  the 
volcano,  causing  the  alterations  in  their  form  which  have  been  noticed.* 

It  was  the  rush  of  the  great  sea- waves  over  the  land,  caused  by  the  violent 

*  It  is  probable  that  lateral  eruptions  contribnted  to  the  alterations  produced  bj  the  ejection  of 
materialfl  from  the  central  crater. 

E 


26  PROF.  JUDD  ON  THE  VOLCAKIC  PHENOMENA. 

eviscei'ation  of  the  crater  of  Krakatoa  aided  by  the  impact  upon  the  water  of  the 
Strait  of  the  enormous  masses  of  falling  material,  that  caused  the  great  destruction 
of  life  and  property  in  the  Strait  of  Sunda.  By  the  inrush  of  these  waves  on  to 
the  land,  all  vessels  near  the  shore  were  stranded,  the  towns  and  villages  along 
the  coast  devastated,  two  of  the  lighthouses  swept  away,  and  the  lives  of  36,380  of 
the  inhabitants,  among  whom  were  37  Europeans,  sacrificed.  The  first  waves 
reached  both  the  Javan  and  the  Sumatran  coasts  between  6  and  7  on  the  evening  of 
August  the  26th,  and  these  probably  mark  the  time  of  the  first  influx  of  water  into  the 
igneous  focus.  A  succession  of  small  oscillations  of  the  sea  continued  all  night,  but 
the  waves  that  followed  the  four  great  explosions  of  5.30,  6.44,  10.2,  and  10.52  in 
the  morning  of  August  the  27th,  were  undoubtedly  the  highest  and  most  destructive  of 
all.  The  question  of  the  nature  and  height  of  these  waves,  and  the  phenomena  which 
accompanied  them,  are  discussed  in  a  subsequent  part  of  this  report.  The  areas 
submerged  by  these  great  waves  is  shown  on  the  Chart,  Fig.  9,  p.  17. 

Early  on  the  morning  of  August  the  27th,  another  phenomenon  began  to  manifest 
itself.  The  vast  quantity  of  watery  vapour  thrown  into  the  atmosphere  during 
the  afternoon  of  the  26th  and  the  night  of  the  26th  and  27th  of  August,  had  reached 
an  excessive  height.  This  height  has  been  estimated  by  Mr.  Joly  at  17  and  possibly 
even  23  miles,  and  by  M.  Fulmmariox  at  12]^  miles.  This  mass  of  vapour  and  dust, 
as  so  graphically  described  by  Captain  Wooldridge,  of  the  Sir  R,  SalCy  on  reaching 
the  limit  of  its  elevation  spread  itself  out  laterally,  giving  rise  to  the  '"  pine-tree " 
appearance  so  familiar  to  the  Itjdians,  who  are  in  the  habit  of  watching  the 
paroxysmal  outbursts  of  Vesuvius.  All  night  long  this  great  cloud  spread  itself 
laterally,  the  particles  of  dust  slowly  descending  through  the  atmosphere.  Between 
10  and  11  a.m.  the  three  vessels  then  at  the  eastern  entrance  of  the  Strait 
encountered  the  fall  of  mingled  dust  and  water,  which  soon  darkened  the  air  and 
covered  their  decks  and  sails  with  a  thick  coating  of  mud.  Some  of  the  pieces 
of  pumice  falling  on  the  Sir  R.  Sale  were  said  to  have  been  of  the  size  of  a  pumpkin. 

Between  10  and  10.30  a.m.  the  same  state  of  things  is  reported  in  Lampong  Bay, 
the  G.  G.  Loudon  being  compelled  at  the  latter  hour  to  come  to  anchor  on  account  of 
the  darkness. 

At  Batavia,  situated  about  100  English  miles  from  Krakatoa,  the  sky  was  clear 
at  7  a.m.,  but  began  to  darken  between  that  hour  and  10  a.m. ;  at  10.15  the  sky 
became  lurid  and  yellowish,  and  lamps  began  to  be  required  in  the  houses ;  about 
10.30  the  first  falls  from  the  overhanging  clouds  took  place  in  the  form  of  fine 
watery  particles,  and  this  was  succeeded  by  a  few  grains  of  dust ;  at  1 1  a,m.  this 
increased  to  a  regular  dust-rain,  becoming  heavier  till  11.20,  when  complete 
darkness  fell  on  the  city.  This  heavy  dust-rain  continued  till  1,  and  afterwards 
less  heavily  till  3  p.m.  The  dust  fell  in  small  rounded  accretions,  containing  about 
10  per  cent,  of  water.  A  similar  phenomenon  is  recorded  as  having  been  observed 
during  the  recent  eruptions  of  Tarawera  in  New  Zealand. 


PROF.  JCJDD  ON  THE  VOLCAKIC  PHENOMENA.  27 

At  Buitenzorg,  a  little  farther  from  the  volcano,  similar  phenomena  were 
recorded  but  were  of  shorter  duration.  The  dust-fall  commenced  at  11,  but 
darkness  did  not  begin  till  noon,  and  it  passed  away  as  the  dust-fall  ceased  at  2  p.m. 
The  darkness,  however,  extended-  in  the  country  eastward  as  far  as  Tjandjer,  about 
130  English  miles,  and  Bandong,  nearly  150  miles  from  the  volcano. 

The  air-waves  produced  by  the  great  explosions  appear  to  have  been  of  three 
kinda  Those  which  were  of  sufficient  rapidity  of  alternation  to  give  rise  to  sounds, 
are  recorded  as  being  heard  as  far  away  as  Rodriguez  and  Diego  Garcia,  which 
are  respectively  3,080  and  2,375  English  miles  distant  from  the  volcano.  Other 
waves  of  larger  dimensions  caused  the  bursting  in  of  windows,  and  even  the  cracking 
of  walls  100  miles  away  at  Batavia  and  Buitenzorg.  Lamps  were  thrown  down, 
gas-jets  extinguished,  and  a  gasometer,  under  the  influence  of  one  of  these  great 
waves,  leaped  out  of  its  well,  causing  the  gas  to  escape.  Even  at  much  greater 
distances  cracks  were  produced  in  walls,  and  all  accounts  agree  in  ascribing  the 
result  to  air-vibrations  and  not  to  earthquakes. 

The  air-vibi-ations  of  still  greater  w6,ve-length  which  travelled  several  times 
round  the  globe,  as  was  first  shown  by  General  Strachey  and  Mr.  Scott,  are  fully 
discussed  in  another  part  of  this  report,  in  which  also  details  are  given  respecting 
the  air-waves  producing  sound.     (See  Part  II.,  p.  58.) 

Eruptive  action  appeared  to  continue  in  the  neighbourhood  of  Krakatoa  during 
the  whole  of  Monday,  the  27th,  though  the  darkness  which  prevailed  over  the  Strait 
of  Sunda  prevented  the  exact  nature  of  the  operations  going  on  there  from  being 
determined.  Three  vessels,  the  Charles  Bal,  the  Sir  R.  Sale,  and  the  NorJiam  Castle^ 
were  all  day  beating  about  in  the  darkness  at  the  eastern  entrance  of  the  Strait,  the 
pumice-dust  falling  upon  them  in  such  quantities  as  to  employ  the  crews  for  hours  in 
shovelling  it  from  the  decks  and  in  beating  it  from  the  sails  and  rigging.  On  board 
the  G.  G.  LoudoUy  anchored  in  Lampong  Bay,  it  is  recorded  that,  after  the  rain  of 
pumice-stone  in  the  early  morning,  only  dust  and  water  fell  in  the  form  of  mud,  which 
accumulated  on  the  deck  at  the  rate  of  6  inches  in  10  minutes.  Frequent  explosions 
and  vivid  lightning  in  the  neighbourhood  of  Krakatoa  are  recorded.  After  the  great 
outbursts  of  the  early  morning  of  the  27th,  however,  it  appears  that  there  was 
a  lull  for  a  time,  as  at  Buitenzorg  no  explosions  were  heard  during  the  afternoon 
till  7  p.m.  At  this  latter  hour  the  explosions,  as  heard  from  Buitenzorg,  recom- 
menced, increasing  in  violence  till  10  or  11  p.m.,  when  they  again  declined,  and  finally 
ceased  to  be  heard  at  2.30  a.m.  on  Tuesday,  the  28th  of  August. 

On  Wednesday,  the  29th  of  August,  the  G.  G.  Loudon  forced  her  way  through 
the  pumice-laden  seas  passing  from  the  Bay  of  Lampong  through  the  Strait  of 
Lagoendie,  and  then  sailed  round  the  west,  south,  and  east  sides  of  Krakatoa,  and 
thence  on  to  Anjer,  which  place  was  reached  at  4  p.m.  They  found  that  the  whole  of 
the  northern  part  of  the  island  of  Krakatoa  had  disappeared,  and  that  no  smoke  was 
at  that  time  issuing  from  it.     It  was  seen,  however,  that  between  Krakatoa  and  Sebesi 

E  2 


28  PROF.  JUDD  ON  THE  VOLCANIC  PHENOMENA, 

"  a  reef  had  formed,  and  that  various  craters  planted  on  that  reef  were  sending  columns 
of  smoke  on  high." 

On  Wednesday,  29th,  and  Thursday,  30th,  the  Sir  R.  Sale  and  Norham  Castle 
were  working  through  the  Strait  from  the  east,  afud  on  the  latter  day  were  within 
ten  miles  of  Erakatoa.  Neither  of  the  captains  reports  any  kind  of  activity  at 
Krakatoa,  nor  did  either  perceive  the  changes  which  had  taken  place  in  the  island. 

The  steamer  Anerley  passed  through  Sunda  Strait  from  the  east  on  Tuesday  the 
28  th ;  she  kept  close  to  the  Java  shore,  and  reports  no  eruptions  as  taking  place  at 
Exakatoa.  The  peak  of  Krakatoa  was  seen  to  he  in  its  usual  position,  and  no  change 
was  noticed  in  its  form,  or  in  that  of  other  parts  of  the  island. 

Neither  the  captain  of  the  Berhice,  nor  of  the  Wm.  H.  Besse,  which  passed 
through  the  Strait  from  the  west  and  east  respectively  on  August  the  29th  and  30th, 
reports  any  kind  of  action  as  being  heard  on  those  days  in  the  direction  of  Erakatoa. 

Those  on  board  the  Prins  Hendrik,  which  entered  the  Siuida  Strait  on 
September  the  3rd,  noticed  that  from  the  part  which  remained  of  £j:ukatoa,  from 
Lang  and  Verlaten  Islands,  from  Steers  and  Calmeyer  Islands,  smoke  continually 
arose,  and  now  and  then  a  flame  was  seen  at  night. 

Commander  Doorn  of  the  Hydrograaf  has  suggested,  from  his  inspection 
of  the  locality  at  a  later  date,  that  the  steam  proceeding  from  the  hot  pimiice 
had  been  mistaken  for  eruptive  outbursts,  but  there  are  some  grounds  for  believing 
that  lateral  eruptions  did  take  place  on  the  flanks  of  Erakatoa  after  the  outburst 
from  the  central  crater  had  entirely  ceased. 

The  soundings  after  the  eruption  indicate,  as  already  pointed  out,  that  a  great 
depression  or  fissure  had  been  formed  in  the  sea-bottom,  extending  eastward  of 
Erakatoa  for  a  distance  of  about  7  or  8  miles,  and  extending  nearly  in  the  direction 
of  the  great  line  of  volcanic  activity  which  traverses  Java  and  Sumatra.  The 
formation  of  the  islands  of  Steers  and  Calmeyer  appears  to  be  most  naturally 
accounted  for  if  we  imagine  that  two  or  more  parasitical  volcanic  cones  had  grown 
up  on  the  northern  flank  of  the  Erakatoa  volcano  and  had  increased  in  size  till 
they  rose  above  the  sea-level.  In  this  state  they  appear  to  have  been  seen  by 
those  on  board  the  G.  O.  Loudon  on  August  the  28th  ;  and  in  a  later  stage  of 
degradation  by  those  on  board  the  Prins  Hendrik,  on  the  3rd  of  September* 
These  cones  of  loose  pumice  on  rising  above  the  sea-level  were  soon  attacked  by 
the  waves,  and  as  in  the  analogous  well-known  cases  of  Graham's  Island  and 
Sabrina,  were  gradually  reduced  first  to  sand-banks  and  then  to  shoals.* 

*  The  excessive  quantity  of  material  which  mnst  have  been  deposited  in  the  channel  between 
Erakatoa  and  Sebesi,  to  cause  the  formation  of  the  two  new  islands  and  the  snrroTmding  shoals,  has 
given  rise  to  the  suggestion  that  large  portions  of  the  volcano  were  actually  hurled  bodily  into  the  air, 
and  fell  into  the  chfumel  in  question.  But  it  is  not  necessary  to  adopt  so  improbable  an  hypothesis 
as  this,  when  we  remark  the  frequency  of  lateral  eruptions  upon  volcanoes,  and  that  we  have  in  this 
case  some  direct  evidence  that  small  parasitical  cones  did  actually  exist  at  this  point  immediately 
after  the  great  outburst. 


PROF.  JUDD  ON  THE  VOLCANIC  PHENOMENA.  29 

There  is  considerable  doubt  as  to  whether  several  small  eruptions  did  not  occur 
in  and  about  Krakatoa  after  the  great  outburst  had  died  out  on  the  28th  or  29th 
of  August.  The  investigations  by  Mr.  Verbeek,  however,  have  established  the  fact 
that  a  not  inconsiderable  explosion,  accompanied  by  a  rumbling  sound,  the  ejection 
of  large  quantities  of  black  mud,  and  a  heavy  sea- wave  certainly  took  place  at  9.30  p.m. 
on  the  10th  of  October.  The  materials  thrown  out  in  this  last  exhibition  of  activity 
were  afterwards  clearly  seen  covering  the  slopes  of  the  peak  of  Krakatoa,  and  the 
Island  of  Calmeyer,  and  the  outburst  must  have  been  a  by  no  means  insignificant  one. 

Judged  of  by  the  quantity  of  materials  ejected,  or  by  the  area  and  duration 
of  the  darkness  caused  by  the  volcanic  dust,  the  eruption  of  Krakatoa  must  have 
been  on  a  much  smaller  scale  than  several  other  outbursts  which  have  occurred 
in  historic  times.  The  great  eruptions  of  Papandayang  in  Java,  in  1772,  of 
Skaptar  JokuU  (Varmdrdalr)  in  Iceland,  in  1783,  and  of  Tomboro  in  Sumbawa,  in 
1815,  were  aU  accompanied  by  the  extrusion  of  much  lai^er  quantities  of  material 
than  that  thrown  out  of  Krakatoa  in  1883.  The  special  feature  of  this  last 
outburst  of  the  volcanic  forces  was  the  excessively  violent  though  short  paroxysms 
with  which  it  terminated.  In  the  terrible  character  of  the  sudden  explosions 
which  gave  rise  to  such  vast  sea  and  air-waves  on  the  morning  of  the  27th  of 
August,  the  eruption  of  Krakatoa  appears  to  have  no  parallel  among  the  records 
of  volcanic  activity.  The  peculiarity  of  the  phenomena  displayed  during  this 
eruption  is,  I  believe,  to  be  accounted  for  by  the  situation  of  the  volcano,  and  its 
liability  to  great  inrushes  of  the  waters  of  the  sea,  as  the  evisceration  of  the 
crater  opened  a  way  to  the  volcanic  focus.  The  manner  in  which  these  influxes 
of  cold  water  would  first  moderate  the  volcanic  action,  and  as  a  consequence 
give  rise  in  the  end  to  tremendous  and  exhaustive  explosions  of  abnormal  violence, 
I  have  already  endeavoured  to  explain. 


II.    The  Materials  ejected  from  Krakatoa. 

As  some  very  remarkable  atmospheric  phenomena  appear  to  have  followed  the 
great  outburst  of  Krakatoa,  and  these  have  been  thought  by  many  authors  to  have 
owed  their  origin,  either  directly  or  indirectly,  to  materials  thrown  into  the  higher 
strata  of  the  gaseous  envelope  of  our  globe  by  these  prodigious  explosions,  it  may  be 
well  to  inquire  as  to  the  exact  nature  and  state  of  division  of  the  substances  which 
are  known  to  have  been  ejected  from  the  volcano. 

Great  facilities  are  afibrded  to  us  for  studying  the  rocks  of  which  Krakatoa  was 
built  up,  by  the  magnificent  sections  produced  during  the  great  final  outbursts.  A 
fine  volcanic  cone,  between  2,000  and  '3,000  fe^t  in  height,  had  nearly  half  of  its 
mass  blown  away,  and  the  almost  perpendicular  precipices  which  were  thus  fortned 


30  PEOF.  JUDD  ON  THE  VOLCANIC  PHENOMENA. 

exhibit  a  wonderM  succession  of  lavas  and  tufis,  the  whole  bound  together  by  a 
network  of  vertical  and  oblique  dykes.  Never,  perhaps,  have  geologists  had  so 
splendid  an  opportunity  of  studying  the  internal  architecture  of  a  compound 
volcanic  cone,  as  that  which  has  been  afforded  to  them  in  the  splendid  ruin  of  Rakata. 
{See  Plate  II.,  Fig.  2.)  The  remaining  slopes  of  the  cone  of  Rakata  are  thickly 
buried  under  masses  of  pumice  and  other  ejected  materials,  in  which  streams  have 
cut  deep  radiating  ravines.     {See  Plate  II.,  Fig.  I.) 

Underneath  this  ruin  of  the  cone  of  Eakata,  the  older  rock-masses  of  the  island 
are  seen  making  their  appearance.  I  am  much  indebted  to  M.  Reni^  Br^n,  who 
visited  the  district  a  few  months  after  the  great  eruption,  for  carefully  selected 
specimens  of  all  the  different  types  of  rock  exhibited  in  the  interior  of  Krakatoa. 

T/ie  Lavas. 

The  great  bulk  of  the  old  crater-ring  of  Ejrakatoa  is  made  up  of  massive 
outflows  of  an  enstatite-dacite,  which  was  found,  on  analysis,  to  contain  6  9 '7  4 
per  cent,  of  silica.  While  the  minerals  contained  in  this  rock  are,  on  the  whole, 
similar  to  those  of  the  enstatite-andesites  so  abundant  in  Java  and  Sumatra — 
namely,  plagiodase  felspar,  ferriferous  enstatite  (hypersthene),  augite,  and  magnetite 
— the  proportion  of  the  base  to  the  included  crystals  appears  to  be  very  different 
in  the  two  cases.  The  Krakatoa-rock  contains  at  least  90  per  cent,  of  base  to 
10  per  cent,  of  crystals ;  and  as  this  base  is  of  a  much  more  acid  character  than 
the  crystals  themselves,  the  Krakatoa  rock  has  a  silica  percentage  of  70,  while  the 
ordinary  andesites  of  Java  and  Sumatra,  which  contain  a  very  much  smaller 
proportion  of  base  to  included  crystals,  contain  only  between  52  and  6 1  parts  in 
100  of  silica.  {See  Plate  III.,  Fig.  1.)  We  have  here  a  very  instructive  illustration 
of  the  necessity  of  taking  into  account,  not  only  the  species  of  minerals  contained 
in  a  rock,  but  the  propoi*tions  in  which  they  are  present.  A  rock  of  very  similar 
character  to  that  so  abundant  at  Krakatoa  was  described  as  occurring  at  Java's 
First  Point  and  Princes  Island  by  MM.  Vbrbebk  and  Fennema,  and  such  highly 
acid  varieties  were,  perhaps,  characteristic  of  the  ejections  from  the  transverse 
fissures  of  the  Strait  of  Sunda. 

These  older  lavas  are  sometimes  compact  and  at  other  times  vesicular.  In 
the  latter  case  the  cavities  are  remarkable  for  the  fine  crystals  of  tridymite, 
sometimes  accompanied  by  hornblende  and  quartz,  which  they  contain;  these 
have  been  described  and  %ured  by  Professor  VoM  Rath.  *  The  crystals  of 
tridymite  appear  to  me  to  be  of  secondary  origin,  and  to  have  been  developed  in 
the  cavities  of  the  rock  by  the  passage  of  acid  vapours. 

The  base  of  these  old  lavas,  which  is  of  a  reddish-brown  colour,  is  seen  under  the 

*  '  VerhandluBgen  des  natnrli.  Vereitis  de  preuss.  Rheinl.  tl.  Wesfcf.,'  1884,  pp.  326-333.     Taf. 
v5.,  flg.  18 


PROF.  JUDD  ON  THE  VOLCANIC  PHENOMENA.  31 

microscope  to  consist  of  glass  crowded  with  microlites  of  felspar,  augite,  enstatite  and 
magnetite,  the  latter  often  converted  into  flecks  of  hydrous-brown  oxide  which  give 
the  rock  its  peculiar  tint.  What  are  believed  to  be  microlites  of  tridymite  have  also 
been  described  as  occurring  in  the  base  of  the  rock.  {See  Plate  III.,  Fig.  2.)  The 
porphyritic  crystals  of  felspar,  enstatite,  augite,  and  magnetite  are  similar  to  those 
found  in  the  later  rocks  of  Krakatoa,  which  will  be  noticed  more  ftdly  hereafter. 

In  the  walls  of  the  old  crater-ring  of  Krakatoa  (as  at  Polish  Hat  and  the 
south  end  of  Lang  Island),  and  among  the  materials  that  have  been  ejected 
within  it,  there  are  found  also  some  very  interesting  porphyritic  pitchstones  of  a 
velvety-black  colour.  These  rocks  are  proved  by  analysis  to  have  precisely  the 
same  chemical  composition  as  the  associated  stony  lavas.  The  included  porphyritic 
crystals  are  also  precisely  the  same.  These  rocks,  except  for  the  proportion  of  the 
glassy  base  to  the  crystals,  bear  a  very  striking  resemblance  to  the  "porphyritic 
pitchstones"  of  the  Cheviot  Hills  which  have  been  made  so  well  known  to 
petrologists  by  the  descriptions  of  Mr.  Teall  and  Dr.  Peterssen.  The  glassy 
base  of  these  rocks  is  of  a  rich  brown  colour  by  transmitted  light,  and  is  crowded 
with  microlites,  a  beautiful  fluidal  structure  being  often  exhibited  in  it.  {See  Plate  III., 
Fig.  4.)  In  certain  parts  of  the  Cheviot  Hills  I  have  found  a  stony  lava  very 
similar  in  appearance  to  that  forming  the  bulk  of  the  crater-ring  of  Krakatoa, 
passing  at  the  surfaces  of  the  lava-streams  into  the  well-known  velvety -black 
porphyritic  pitchstone  of  the  district,  and  it  is  probable  that  similar  relations  exist 
between  the  analogous  rocks  at  Krakatoa.  With  these  lavas  only  very  insignificant 
beds  of  tuff  have  been  found  associated. 

The  next  lavas  ejected  at  Krakatoa  present  a  very  striking  difference  from  those 
just  described.  They  are  seen  in  the  great  lateral  peak  of  Rakata,  which  was  built  up 
by  a  succession  of  eruptions  from  a  vent  opened  on  the  edge  of  the  great  crater. 
The  unconformity  of  these  basaltic  lavas,  and  of  the  tuffs  of  the  same  composition 
alternating  with  them,  to  the  older  dacites  is  well  seen  in  the  great  natural  section 
produced  by  the  eruption  of  1883.  {See  Plate  II.,  Fig.  2.)  These  basalts  do  not  offer 
much  subject  for  remark  ;  some  appear  to  contain  much  greater  proportions  of  olivine 
than  others,  and  there  are  variations  in  the  degree  of  crystallization  of  the  materials. 
A  specimen  which  was  analysed  gave  a  percentage  of  48*81  of  silica. 

With  the  eruption  of  the  materials  which  covered  the  lower  and  northern  part 
of  Krakatoa  we  find  a  return  to  the  earlier  types  of  lavas.  They  all  consist  of 
enstatite-dacites  with  about  70  per  cent,  of  silica.  Indeed  the  ultimate  chemical 
composition,  and  the  nature  of  the  porphyritic  crystals  embedded  in  these  youngest 
lavas  are  so  similar  to  those  of  the  earliest  period,  that  the  re-fusion  and  outwelling 
of  some  of  the  lower  portions  of  the  mass  are  very  strongly  suggested  by  their 
study. 

Concerning  the  materials  thrown  out  during  the  last  eruption  of  Krakatoa,  we 
have  fortmiately  a  large  number  of  valuable  observations  made  both  by  chemists  and 


32 


PROF.  JUDD  ON  THE  VOLCANIC  PHENOMENA. 


by  mineralogists  ;  and  the  study  of  these  materials  is,  I  believe,  calculated  to  cast 
much  new  light  upon  certain  vulcanological  problems. 

Mr.  Verbeek  computes  that  of  the  materials  thrown  out  between  May  the  20th 
and  the  period  when  the  whole  solid  framework  of  the  interior  of  the  volcano  was 
blown  up,  at  least  95  per  cent,  consisted  of  pumice  and  dust,  and  not  more  than  5  per 
cent,  was  made  up  of  compact  lava  and  of  fragments  torn  from  the  side  of  the  vent. 
As  the  pumice  and  dust  were  all  formed,  as  we  shall  see,  from  the  compact  lava,  it 
will  be  convenient  to  describe  this  at  the  outset. 

The  compact  lava  of  1883  presents  itself  under  two  diflferent  forms,  the  distinc- 
tions between  which  are  worthy  of  the  most  carefiil  study.  These  two  rocks  may 
be  characterised  as  porphyritic  pitchstone,  and  porphyritic  obsidian.  In  both  these 
the  crystalline  elements  are  the  same,  and  constitute  only  about  10  per  cent,  of  the 
whole  bulk  of  the  rock.  Of  these  crystalline  elements  felspar  constitutes  about 
two-thirds,  crystals  of  pyroxene  about  one-third  as  much  as  the  felspar,  and  magnetite 
about  half  the  bulk  of  the  pyroxenes.  The  crystals  do  not  appear  to  be  scattered 
by  any  means  uniformly  through  these  rocks,  but  little  groups,  each  containing  a 
number  of  crystals  of  felspar,  pyroxene,  and  magnetite  are  found  at  intervals  in  the 
ground-mass.  The  pyroxenes  include  the  two  different  forms,  a  rhombic  pyroxene  or 
enstatite,  and  a  monoclinic  form  or  augite ;  the  former  appearing  to  be  about  twice 
as  abundant  as  the  latter.  In  addition  to  the  essential  minerals  of  the  rock,  apatite, 
pyrite,  and  pyrrhotine  (magnetic  pyrites)  were  found  to  occur  in  small  quantities  as 
accidental  or  accessory  constituents.  Perhaps  the  most  striking  feature  of  these 
rocks  is  the  large  proportion  borne  by  the  base  to  the  crystalline  elements  diffused 
through  it. 

The  average  composition  of  this  rock  is  probably  well  represented  by  an  analysis 
made  by  Professor  C.  Winkler,  of  Freiberg,  in  Saxony,  of  a  mass  of  the  Krakatoa 
pumice,  collected  by  Mr.  Verbeek  upon  the  island  on  October  the  16th,  1883.  Its 
specific  gravity  was  found  to  be  2-329.     Omitting  the  moisture  and  substances  soluble 


composition  was  loi 

ana  to 

be  as  ic 

allows  :— 

- 

Silica 

68-99 

Titanic  acid 

0-82 

Alumina    ., 

16-07 

Ferric  oxide 

2-63 

Ferrous  oxide 

1-10 

Manganous  oxide. 

0-28 

Lime          •  • 

3-16 

Magnesia  . . 

1-08 

Potash 

1-83 

Soda 

4-04 

100  00 

PROF.  JUDD  ON  THE  VOLCANIC   PHENOMENA. 


S3 


Mr.  J.  W.  Retgebs,  of  Buitenzorg,  taking  the  dust  which  fell  at  that  place, 
which  was  very  carefully  collected  so  as  to  avoid  accidental  admixtures,  and  employing 
the  most  delicate  and  refined  methods  for  separating  the  particles  of  glass  from  those 
of  crystalline  minerals,  and  the  several  varieties  of  the  latter  from  one  another,  has 
been  able  to  isolate  and  analyse  the  several  constituents  of  these  rocks.  His  results 
are  given  in  the  following  table.  The  optical  and  other  characters  of  the  minerals  of 
these  rocks,  as  exhibited  in  the  dust  derived  from  them,  also  have  been  studied  by 
Richard,*  RENARD,t  Sauer,J  H.  H.  Reusch,§  OebbkkeJ  Von  Lasaulx,!  Carvtll 
Lewis,**  JoLY,tt  Waller,^!:  R.  BRfiON,§§  and  myself,  |||!  as  well  hs  by  MM.  Verbeek, 
Rexgers,  and  Winkler.  If H 


Glass. 

Felspae. 

Enstatitb. 

AfGlTE. 

Magnetitk. 

(All  materials 

having  a 

Average  of 

Highly 

specific 

all  kinds 

ferriferous. 

(With 

gi^avity  less 

present. 

(Amblyste- 

Ilmenite.) 

than  2G.) 

gite). 

Silica 

68-12 

58-29 

52-3 

48-6 

Titanic  Acid 

0-18 

— 

— 

— 

6-7 

Alumina     . . 

15-81 

27-19 

6-1 

8-2 

— 

Ferric  Oxide 

)        5-01 

— . 

— 

— 

66-0 

Ferrous  Oxide 

— 

27-7 

14-0 

37-3 

Manganoas  Oxide 

— 

— 

trace. 

— 

— 

Lime 

2-78 

8-27 

2'2 

18-9 

— 

Magnesia  . . 

1-18 



13-6 

11-6 

— 

Potash 

1-06 

1-22 

— 

— 

— 

Soda          

5-09 

6'82 

— : 

— 

y9-23 

100-79 

101-9 

101-3 

lOO-O 

With  respect  to  the  felspars  of  those  rocks,  MM.  Verbeek  and  Retgebs  have 
arrived  at  the  interesting  conclusion  that  all  the  varieties  of  plagioclase  are  present 
together  in  the  same  mass.     They  conclude  that  85  per  cent,  of  the  felspar-crystals, 


•  '  Comptes  Rendus.'     Seance  du  19  Novembre,  1883. 

t  'Bnll.  de  I'Acad.  Royale  de  Belgique/  3itoe  Ser.,  t.  vi.,  1883. 

X  *  Berichte  der  Natnrf .  Gesellsch.  zn  Leipzig,'  1883,  p.  87. 

§  *Nenes  Jahrb.  fiir  Min.,*  Ac,  1884,  I.  Bd.,  p.  78. 

II  *  Nenes  Jahrb.  liir  Min.,'  Ac,  1884,  II.  Bd.,  p.  32. 

T  *Sitzg.  d.  niederrh.  Ges.  in  Bonn'  (Sitzg.  vom  3  December,  1883). 

••  '  Proc.  Acad.  Nat.  So.,'  Philadelphia,  1884,  p.  185. 

tt  *  Royal  Dablin  Society,'  N.S.,  vol.  4,  p.  291. 

XX  *  Birm.  Nat.  Hist,  and  Microscop.  Soc,  Rep.  and  Trans,  for  1883,'  p.  vi.  (March  4th,  1884J. 

§§  'La  Nature,'  13«^«  Annee  (1885),  p.  373. 

nil  'Nature,'  vol.  xxix.,  p.  595. 

It  *  Krakatau,'  pp.  185-324. 

F 


^i  PROF.  JUDD   ON   THE   VOLCAXIC   PHENOMENA. 

however,  are  llrae- soda  felspars,  intermediate  between  the  very  acid  and  the  very  basic 
types,  and  would,  according  to  the  ordinary  mineralogical  nomenclature,  be  ranked 
as  labradorite,  andesine,  or  oligoclase.  Smaller  quantities  of  anorthite,  albite,  and 
potash-plagioclase  (anorthoclase  of  Rosenbusch),  also  are  found  in  the  rock.  These 
results  are  of  very  great  interest  to  petrographers.  Many  rocks  have  been  shown  to 
contain  felspars  belonging  to  more  than  one  species ;  the  felspars  of  the  first  and 
second  consolidation  in  a  rock,  indeed,  usually  differ  considerably  in  composition.  In 
the  same  crystal,  too,  we  may  find  a  number  of  successively  formed  zones,  having 
different  chemical  composition  and  optical  properties  ;  and  crystals  of  plagioclase  mar 
be  found  actually  surrounded  by  a  zone  of  orthoclase.  Never,  however,  as  far  bs  I 
am  aware,  has  so  great  a  diversity  of  felspar-crystals  been  recorded  in  the  same  rock 
as  in  that  of  Krakatoa.  It  must  be  remembered,  however,  that  the  conclusion  of 
MM.  Verbeek  and  Retoers  is  founded,  not  on  the  study  of  a  rock  itself,  but  on 
the  dust  produced  by  the  comminution  of  great  masses  of  rock  in  which  considerable 
diversity  of  mineralogical  constituents  may  have  existed  The  felspar-crystals  of  the 
Krakatoa-rocks  are  usually  remarkable  for  the  striking  zoned  structure  exhibited  by 
the  individual  cr}-stals. 

The  enstatite  of  these  rocks  is  of  a  deep  tint  and  highly  pleochroic  According 
to  the  analysis  of  M.  Ketgers,  indeed  it  must  be  regarded  as  containing  a  higher 
percentage  of  iron  than  the  ordinary  hypersthenes  ;  and  if  we  follow  the  nomen- 
clature which  I  have  suggested  for  the  varieties  of  enstatite,  it  should  be  classed 
as  an  amblystegite. 

The  augite,  which  is  aluminous  and  contains  a  high  percentage  of  lime,  is  of  a 
pale  olive-green  tint  and  exhibits  only  a  very  feeble  pleochroism.  Examples  of 
intergrowth  of  the  monoclinic  augite  and  the  rhombic  enstatite,  the  corresponding 
axes  of  the  two  crystals  being  in  parallel  positions,  are  not  unfrequent. 

In  addition  to  magnetite,  in  these  rocks  there  have  been  found  ilmenite,  pyrite, 
pyrrhotine,  apatite,  and  some  secondary  products. 

There  ia  often  a  marked  contrast  between  the  porphyritic  felspar-crystals  embedded 
in  the  two  types  of  glassy  dacite  rocks.  In  the  obsidians,  the  crystals  of  felspar 
have  sometimes  perfectly  sharp  outlines  ;  they  contain  glass-cavities,  often  with  the 
rectangular  outlines  of  negative  crystals,  containing  gas  bubbles.  The  broMTi  glass 
filling  these  cavities  is  much  darker  in  colour  than  the  glass  of  the  ground-mass, 
though  traces  of  a  similar  brown  glass  are  often  seen  adhering  to  the  sides  of  the 
knots  of  crystals  {See  Plate  III.,  Fig.  5).  The  crystals  are  not  unfrequently  broken, 
and  are  sometimes  bent;  in  the  latter  case  the  development  of  the  lamellar  twinning  in 
them  is  seen  to  have  been  determined  by  the  strain  to  which  they  had  been  subjected. 

In  the  pitchstones,  the  felspar-crystals  more  frequently  have  their  angles  and  edges 
rounded,  and  through  the  whole  of  their  interior  a  great  amount  of  corrosion  has 
taken  place,  so  that  the  crystals  now  appear  as  mere  skeletons,  the  glass  which  has 
eaten  into  the  crystals  being  much  greater  in  bulk  than  the  crystalline  material  that 


PROF.  JUDD  ON  THE  VOLCANIC  PHENOMENA.  35 

remains.  In  eating  into  the  substance  of  the  crystals  the  corrosive  material  has 
evidently  taken  advantage  of  planes  of  chemical  weakness  in  the  crystals ;  but  it 
is  remarkable  that  in  many  cases  there  is  an  outer  zone  which  remains  almost  intact. 
{See  Plate  III,  Fig.  3.*) 

Let  us  now  turn  our  attention  from  the  crystals  scattered  through  these  rocks, 
to  the  base,  or  ground-mass,  in  which  they  are  embedded. 

The  porphyritic  pitchstone  of  the  1883  eruption  appears  to  be  almost  absolutely 
identical  in  its  characters  with  the  older  material  already  referred  to  as  forming  Polish 
Hat  Island,  and  also  occurring  at  the  south  end  of  Lang  Island  and  other  points  in  the 
old  crater-ring.  (See  p.  31.)  It  is  black  and  perfectly  opaque,  except  in  very  thin  sec- 
tions, and  has  a  resinous  lustre.  Under  the  microscope  the  base  of  the  pitchstones 
is  seen  to  be  formed  of  a  felted  mass  of  microlites  of  felspar  and  pyroxene,  with  grains 
of  magnetite,  and  the  whole  mass  has  its  interstices  filled  with  a  yellowish  or  brown 
glass.    The  base  often  exhibits  a  banded  or  fluidal  structure.    {See  Plate  III.,  Fig.  4.) 

The  porphyritic  obsidian  on  the  other  hand  has  a  strikingly  vitreous  lustre.  By 
reflected  light  it  is  of  a  very  dark  brown,  nearly  black,  colour ;  by  transmitted 
light,  of  a  rich  yellowish-brown  tint ;  while  in  thin  sections  it  is  almost  colourless. 
In  the  midst  of  this  glass  may  be  seen  a  very  few  scattered  microlites  of  ftkpar 
and  pyroxene,  these  bearing  but  a  very  small  proportion  indeed  to  the  glass  in 
which  they  are  enclosed,  and  in  this  respect  the  obsidians  offer  a  very  striking  contrast 
to  the  pitchstones  above  described,     {See  Plate  III.,  Fig.  6.) 

Occasionally,  however,  rocks  are  found  which  are  intermediate  in  the  characters 
of  their  base  between  the  obsidians  and  the  pitohstones. 

The  most  striking  differences  between  these  two  rocks  are  seen,  however,  when 
they  are  subjected  to  a  high  temperature.  Before  a  gas-flame,  urged  by  a  foot-blast, 
the  pitchstone  is  found  to  decrepitate,  but  to  undergo  fusion  only  with  the  greatest 
difficulty.  The  obsidian,  on  the  other  hand,  is  fused  with  comparative  ease,  and 
during  fusion,  bubbles  and  swells  up  into  cauliflower-like  masses,  which  will  float  on 
water.  These  white  cauliflower-shaped  masses  have  exactly  the  colour  and  appearance 
of  the  pumice  ejected  from  Krakaloa,  and  on  making  thin  sections  of  them  and 
comparing  them  with  sections  of  the  Krakatoa-pumice,  their  structtu'e  is  found  to  be 
almost  absolutely  identical.  {See  Plate  IV.,  Fig.  4.)  The  loss  suffered  by  the  pitch- 
stones on  ignition  is  almost  nil,  while  the  obsidians  lose  from  I,  to  5  or  6  per  cent,  of 
their  weight. 

In  the  case  of  the  curious  marekanite  of  Siberia,  and  of  a  mica-dacite  glass 
from  Fifeshire,  I  have  already  pointed  out  the  tendency  of  glasses  containing  large 
quantities  of  water  to  undergo  fusion  at  comparatively  low  temperatures,  and  while 
doing  so  to  part  with  their  volatile  ingredients,  becoming  thereby  converted  into 
pumice.t 

•  The  Plates  IT.,  III.,'  and  IV.  will  be  found  at  the  end  of  tbis  Part,  i.e.,  after  p.  56. 
t  '  Quart.  Jour.  Geo.  Soc.,'  vol.  xlii.  (1886),  p.  429 ;  *  Gaol.  Ma^.,'  Doc.  iii.,  vol.  iii.  (1S86),  p.  243. 

F  2 


3G  PROF.  JUDD   OX   THE  VOLCANIC   PHENOMENA. 


Tfie  Pumice. 

The  pumice  which  was  thrown  out  in  such  enormous  quantities  during  the  latest 
eruption  of  Krakatoa,  was  evidently  formed  by  the  disengagement  of  volatile  matters, 
throughout  the  whole  substance  of  this  obsidian.  The  formation  of  this  pumice  can 
indeed  be  exactly  imitated  if  we  take  a  strong  solution  of  bicarbonate  of  soda, 
rendered  slightly  viscous  by  the  addition  of  gum,  and  made  neaily  opaque  by  the 
addition  of  some  brown  colouring  matter,  and  allow  an  acid  to  diffuse  itself  through 
the  mass.  The  carbonic  acid,  as  it  becomes  disengaged,  will  distend  the  whole 
mass  to  five  or  six  times  its  original  bulk,  owing  to  the  formation  of  gas  bubbles 
in  its  midst,  and  we  get  a  white  mass  of  froth  exactly  resembling  pumice.  Nothing 
can  be  more  certain  than  the  fact  that  the  volatile  substances  which,  escaping  in 
puch  quantities  from  the  vent  of  Krakatoa,  gave  rise  to  the  last  eruption,  were 
originally  imprisoned  in  every  part  of  the  glassy  mass.  The  whole  of  the  pumiceous 
substance  is  penetrated  with  the  finest  vesicles  produced  by  the  disengagement  of 
gas.  Those  fragments  of  the  lava  which  had  cooled  so  far  as  to  become  con- 
solidated before  ejection,  only  require ^to  be  heated  in  order  to  give  off  their  volatile 
ingredients ;  and  in  doing  so  the  melting  glass  is  converted  into  a  true  pumice.  In 
what  condition  water  and  other  volatile  substances  exist  in  these  glassy  rocks  is  still 
to  some  extent  an  unsolved  problem.  Such  rocks  may  lose  from  1  to  10  per  cent, 
on  ignition.  It  is  certain,  however,  that  the  water  or  other  substances  do  not  exist 
in  any  cavities  visible  under  the  highest  powers  of  the  microscope,  and  it  is  probable 
that  they  are  in  actual  combination  with  the  glass  or  colloid  body. 

The  presence  of  from  3  to  16  per  cent,  of  water  in  opals  or  colloid  silica,  is  probably 
a  perfectly  similar  case.  Colloid  bodies  appear  to  have  this  power  of  taking  up 
and  of  retaining  large  quantities  of  water  and  other  volatile  substances.  The  diflSculty 
of  removing  the  last  traces  of  water  from  precipitated  colloid  silica  is  very  well 
known. 

The  pumice  of  Krakatoa  is  found  presenting  two  different  varieties.  By  far  the 
rarest  of  these  is  a  perfectly  white  material  of  very  fibrous  texture,  closely  resembling 
the  well-known  pumice  of  Lipari.  In  this  variety  porphyritic  crystals  do  not  appear 
to  be  present.  I  received  a  specimen  of  this  variety  from  Mr.  H.  O.  Forbes,  to  whom 
it  was  given  by  one  of  the  party  from  Batavia  that  visited  Krakatoa  on  May  27th, 
1883  ;  the  mass,  which  was  about  2 J  inches  in  diameter,  was  among  the  frag- 
ments thrown  out  during  the  earliest  stage  of  the  eruption.  (See  Plate  IV.,  Figs. 
1  and  2.) 

The  great  mass  of  the  pumice  thrown  out  during  the  eruption,  however,  presented  a 
dirty  greyish-white  tint,  the  air-pores  in  it  being  very  irregular  in  size,  and  sometimes 
large.  Scattered  all  through  the  mass  are  little  knots  of  crystals  of  felspar,  pyroxene, 
and  magnetite,  distributed  at  somewhat  wide  intervals.     When,  as  wa^  usually  the 


PROF.  JUDD   ON   THE   VOLCANIC   PHENOMENA.  37 

case,  the  pumice  was  rounded,  either  by  the  striking  of  fragments  in  the  air  or  by 
their  attrition  while  floating  on  the  ocean,  the  little  knots  of  crystals,  on  account  of 
their  superior  hardness,  stand  out  like  warts  on  the  surfaces  of  the  masses.  In 
addition  to  these  knots  of  crystals  there  are  sometimes  found  little  fragments  of 
black  glass,  and  these,  when  examined  in  thin  sections,  are  seen  to  be  composed  of 
the  pitchstone  already  described,  often  containing  the  usual  porphyritic  crystals, 
which  are  in  such  cases  remarkably  coiToded.     (See  Plate  IIL,  Fig.  3.) 

The  formation  of  this  pumice  by  the  escape  of  imprisoned  volatile  matters  in  the 
obsidian,  while  it  was  still  in  a  viscous  condition,  is  abundantly  illustrated  if  we 
examine  its  structure  microscopically  ;  the  glass  is  seen  to  be  drawn  out  into  plates 
and  threads  of  all  dimensions.  {See  Plate  IV.,  Figs.  1,  2,  3.)  In  specimens  of  pumice 
wluch  were  collected  on  Krakatoa,  and  had  not  been  immersed  in  the  sea-water,  the 
microscope  often  reveals  delicate  fibres  of  spun  glass  running  from  one  side  of  a 
cavity  to  the  other,  and  these  are  frequently  of  the  smallest  dimensions  which  can 
be  recognised  by  the  microscope.  In  this  connection  we  may  recall  the  ingenious 
experiments  of  Mr.  C.  V.  Boys,  who  has  managed  to  draw  out  threads  of  glass  of 
ultra-microscopical  dimensions  ;  the  existence  of  which  could  be  proved,  however,  by 
their  diffraction  effects.*  That  similar  ultra-microscopical  threads  were  formed  in  the 
cavities  of  the  Krakatoa -pumice  we  have  every  reason  for  believing. 

In  order  to  determine  the  amount  of  distension  which  the  ol^sidian  underwent  in 
its  conversion  into  pumice,  rectangular  blocks  of  the  latter  substance  were  cut  and 
careftiUy  measured  and  weighed.  The  tine-grained,  very  dense,  white  pumice  was  found 
to  have  nearly  three  and  a  half  times  the  volume  of  the  glass  out  of  which  it  was 
formed ;  and  the  much  more  common  dirty-grey  pumice  was  found  in  average 
examples  to  have  undergone  a  dilatation  to  five  and  a  half  times  its  original  bulk,  and 
this  in  spite  of  the  fact  that  something  like  one-tenth  of  the  original  lava  consisted 
of  undilatable  crystals,  which  remained  to  weight  the  mass.  Owing  to  the  existence 
of  the  heavy  crystals  diffused  through  it,  and  the  fact  that  water  enters  it  to  some 
extent  by  the  large  open  pores,  the  ordinary  Krakatoa  pumice  was  found  to  float 
with  two-thirds  of  its  bulk  submerged  and  one-third  above  the  water.  Much  of 
the  pumice,  in  which  the  air-cells  were  exceptionally  large,  was  far  more  bulky  in 
proportion  to  its  weight ;  and  some  of  these  pieces  projected  to  enormous  heights 
in  the  atmosphere,  appear  to  have  been  swept  great  distances  by  air-currents  before 
they  finally  fell  into  the  sea. 

The  study  of  the  pumice  of  Krakatoa  shows  that  the  greater  part  of  the  glass  of 
which  it  is  composed  depolarises  light  to  a  greater  or  less  extent.  It  is  evident, 
therefore,  that  it  is  in  a  condition  of  intense  strain,  the  result  of  the  rapidity  with 
which  it  cooled.  To  the  same  cause  must  probably  be  ascribed  its  extreme  brittleness, 
for  it  can  be  easily  crumbled  between  the  fingers. 

In  addition  to  the  analysis  of  the  pumice  of  Krakatoa  published  by  Professor  C. 

•-  *  Phil.  Mag.,'  Series  V.,  vol.  xxiii.  (1887),  p.  489. 


38 


PROF.  JUDD   OX  THE  VOLCANIC  PHENOMENA. 


Winkler,  of  Freiberg,  I  add  the  following,  which  has  been  kindly  furnished  to  me 
by  Mr.  T.  H.  Waller,  of  Birmingham  : — 


Silica 

69  4 

Alumina 

15-9 

Ferric  oxide 

1-2 

Ferrous  oxide 

2-2 

Lime 

3-4 

Magnesia    . . 

11 

Soda            

4-2 

Potash 

2-3 

Loss  on  ignition 

10 

100-7 


The  chloride  of  sodium  and  other  soluble  matter  with  which  the  pumice  was 
impregnated  from  floating  in  sea  water  was  removed  by  washing  before  this  analysis 
was  made. 

As  far  as  I  have  been  able  to  determine,  the  pumice  ejected  from  Krakatoa 
before  and  during  the  last  violent  stage  of  the  eruption  was  identical  in  character. 
As  this  material  was  being  thrown  into  the  sea  during  nearly  four  months,  it  is 
impossible  to  determine  at  what  date  any  particular  specimen  found  in  the  ocean  may 
have  started  on  its  journey,  and  consequently  the  hope  of  determining  the  direction 
ami  rate  of  the  marine  currents  by  which  they  were  distributed  must  be  abandoned. 
It  may  be  added,  that  as  the  Krakatoa- pumice  floats  with  so  large  a  portion  of  its 
mass  above  the  water,  prevalent  winds  might  have  much  influence  in  determining  or 
modifying  its  movements. 

Dr.  C.  Meldrum,  F.RS.,  of  Mauritius,  had  special  facilities  for  collecting 
observations  on  the  subject  of  the  distribution  of  this  pumice,  and  his  notes  on  the 
subject,  which  were  presented  to  the  British  Association,  were  published  in  1885. 
They  are  reproduced  as  an  Appendix  to  this  report,  together  with  a  Memorandum  on 
the  subject  by  Mr.  Robert  H.  Scott,  F.RS.  (pp.  47,  48). 


The  Volcanic  Dust. 


Let  us  now  proceed  to  the  study  of  the  volcanic  dust  which  was  formed  in 
such  enormous  quantities  during  the  Ejrakatoa  eruption. 

That  steam  escaping  from  a  mass  of  molten  glass  may  carry  off  fine  particles  of 
the  substance,  often  dragging  it  out  into  threads,  appears  highly  probable.     That  such 


PROF.   JUDD   OX  THE  VOLCANIC  PHENOMBXA.  39 

is  actually  the  case  I  was  able  to  prove  by  heating  the  little  obsidian-balls  known  as 
"  marekanite,"  when  clouds  of  finely-divided  particles  were  seen  to  be  driven  off  from 
its  mass.  But  the  great  bulk  of  the  volcanic  dust  of  Krakatoa  was  undoubtedly  formed 
by  the  striking  together  of  fragments  of  pumice  as  they  were  violently  ejected  from 
the  crater  and  fell  back  again  into  it.  The  noise  made  by  this  hurtling  of  fragments 
in  the  air  was  remarked  upon  by  several  observers,  and  as  I  have  myself  noticed  at 
Stromboli,  is  often  more  striking  than  the  sound  of  the  explosions.  The  action  of 
this  "  dust-making  "  mill,  as  an  active  volcano  undoubtedly  is,  was  well  illustrated 
during  the  Vesuvian  eruption  of  1822.  Mr.  Scrope,  who  was  an  eye-witness  of  that 
eruption,  describes  how  day  after  day  as  the  eruption  proceeded  ^the  dust-particles 
became  finer  and  finer,  till  at  last  they  were  able  to  penetrate  the  finest  cracks,  finding 
their  way  into  and  filling  all  locked  boxes,  drawers,  and  similar  receptacles. 

The  extreme  brittleness  of  the  glass  of  the  pumice,  which  I  have  before  remarked 
upon,  as  the  result  of  its  sudden  cooling,  would  facilitate  its  pulverization ;  and  as 
it  was  reduced  to  powder  it  would  remain  longer  in  the  atmosphere,  and  be  swept 
ferther  away  from  the  central  ascending  steam-column.  The  large  fragments  of 
pumice  would  be  re-ejected  again  and  again  as  they  fell  back  into  the  crater,  each 
time  being*  reduced  in  bulk  and  weight.  All  the  ejected  blocks  of  pumice  bore 
obvious  marks  in  their  rounded  form  of  this  attrition  in  the  air,  and  the  work  of 
rounding  and  reduction  in  bulk  went  on  after  they  reached  the  ocean,  and  were  swept 
by  currents  and  driven  by  winds. 

If  a  piece  of  the  Krakiatoa  pumice  be  pounded  in  a  mortar,  and  the  dust  so  formed 
be  mounted  and  examined  microscopically,  it  will  be  found  to  agree  in  the  form  of 
its  particles  and  its  general  characters  with  the  volcanic  dust  which  fell  at  so  many 
points  around  the  volcano.     (See  Plate  IV.,  Fig.  6.) 

Through  the  kindness  of  many  correspondents  I  have  had  the  opportunity  of 
studying  a  very  large  number  of  samples  of  the  Krakatoa-dust,  collected  from  many 
points,  ranging  from  40  to  1,100  English  miles  away  from  the  volcano. 

Even  to  the  naked  eye,  striking  differences  are  manifest  among  these  various 
specimens.  Those  collected  nearest  to  the  volcano  obviously  consist  of  coarser 
particles,  and  they  are  of  a  somewhat  darker  tint  owing  to  the  greater  abundance  in 
them  of  fragments  of  crystals,  especially  those  of  magnetite  and  other  dark -coloured 
minerals.  Those  dusts  which  were  collected  at  the  greatest  distance  from  the  volcano 
were  excessively  fine  and  almost  perfectly  white  in  colour.  Professor  Winkler 
describes  the  dusts  which  fell  at  Krakatoa  as  having  a  darker  tint  and  a  higher 
specific  gravity  than  those  which  fell  at  Buitenzorg. 

Under  the  microscope  the  differences  between  the  dusts  collected  at  different 
points  come  out  in  a  very  striking  manner. 

A  considerable  number  of  analyses  of  the  Krakatoa  dust  have  been  made  by 
different  observers,  and  for  the  sake  of  comparison  I  have  placed  three  of  these  side  by 
side.     I  have  in  each  case  rejected  the  volatile  matters  and  calculated  the  totals  to  100, 


^0 


PROF.  JUDD  ON  THE  VOLCANIC  PHENOMENA. 


Analyses  of  the  Dust  of  Krakatoa  which  fell  at  different  distances  from  Krakatoa, 


A. 

B. 

c. 

Dust  which  fell 

Dust  which  fell 

Dnfit  which  fell 

at  points  within 

nearly  900  mites 

at  Krakatoa. 

100  miles  from 

from 

ihe  Volcano. 

the  Volcano. 

Collected  by  Cap- 
tain Ferzeuaar. 

Buitenssorg. 

8.  Barbarosea, 

Prof.  C.  Winkler. 

Prof.  C  Winkler. 

A.  Schwager. 

Silica           

61-36 

66-77 

68-99 

Titanic  Acid 

1-12 

0-67 

0-39 

Alamitia      .... 

17-77 

16-44 

15-24 

Ferric  Oxide 

4-39 

3-41 

0-<?8 

Ferrous  Oxide 

1-71 

1-37 

3-72 

ManganouH  Oxide  . . 

0-41 

0-38 

trace. 

Lime. . 

3-45 

2-90 

2-76 

Magnesia      . . 

2-32 

1-67 

0-83 

Pofcash          

2-51 

2-25 

3-47 

Soda. . 

4-98 

4-14 

4-32 

Let  us  now  consider  the  causes  which  would  affect  the  composition  of  the 
dust  which  fell  at  different  points,  and  at  varying  distances  from  Krakatoa. 

By  the  influence  of  the  great  upward  currents  of  steam,  an  immense  mass  of 
comminuted  particles  of  pumice  would  be  carried  to  the  height  of  many  miles  into 
the  atmosphere.  Nine-tenths  of  this  material  consisted  of  a  glass  having  a  specific 
gravity  of  less  than  2*3,  drawn  out  into  fine  threads  and  thin  plates,  often  hollow  and 
containing  bubbles  of  air,  and  sometimes,  in  all  probabiUty,  reduced  to  particles  of 
ultra-microscopic  dimensions.  These  particles  of  glass  would  tend  to  float  by  the 
adhesion  between  them  and  air,  and,  in  the  higher  and  rarer  portions  of  the  atmo- 
sphere, their  suspension  may  not  improbably  have  been  aided  by  their  mutual  re- 
pulsion resulting  from  a  highly  electrified  condition. 

The  crystalline  particles  in  the  mass  would  consist  of  fragments  of  felspar,  with 
a  specific  gravity  ranging  from  2*54  to  2*75,  of  fragments  of  pyroxene  with  densities 
of  3*3  to  3  "5,  and  of  magnetite,  with  a  density  of  5  0.  The  crystals  of  felspar, 
hypersthene  and  augite  were,  in  the  original  pumice,  of  much  greater  size  than  the 
magnetite.  But  the  easy  double  cleavage  in  the  felspars,  and  to  a  smaller  extent  in 
the  pyroxenes,  would  facilitate  the  reduction  of  these  minerals  to  finer  particles  than 
the  magnetite. 

As  the  particles  travelled  outwards  from  the  centre,  they  would  tend  to  fall, 
therefore,  in   the   following   order: — 1.  Magnetite   (the   hecxviest    and    least   friable 


PROP.  JUDD  ON  THE  VOLCANIC  PHENOMENA.  41 

material) ;  2.  Pyroxenes  (next  in  weight  and  only  moderately  cleavable) ;  3.  Felspar 
(lighter  and  very  cleavable) ;  and  4,  and  last,  the  very  light  and  friable  glass. 

At  all  points,  therefore,  the  dust  which  fell  would  have  a  tendency  to  differ  in 
composition  from  the  pumice  out  of  which  it  was  formed.  Near  the  volcano  the 
abundance  of  the  crystalline  materials  falling,  and  especially  of  the  magnetite  and 
pyroxenes,  would  render  the  dust  darker  in  colour  and  more  basic  in  composition ; 
while  farther  away  the  glass-  and  felspar-particles  which  fell  would  have  a  smaller 
admixture  of  the  more  basic  materials.  A  certain  proportion  of  the  glass,  including 
the  Tiltra-microscopical,  the  elongated,  and  the  very  thin  particles,  would  float  almost 
indefinitely,  and  would  not  find  any  place  in  the  masses  of  dust  coUected  around  the 
volcano. 

Besides  this  it  must  be  recollected  that  there  are  always  particles  of  both 
Clonic  and  inorganic  dust  floating  in  the  atmosphere,  and  these  would  be  carried 
down  mingled  with  the  volcanic  materials.  In  every  sample  of  Krakatoa-dust 
which  I  have  examined,  these  ordinary  constituents  of  the  atmosphere  could  be 
detected. 

Further  than  this,  the  steam  issuing  fi-om  the  volcano  was  mingled  with  both 
hydrochloric  and  sulphurous  acids,  the  latter  taking  up  oxygen  and  passing  into 
sulphuric  acid.  By  these  powerful  acids  the  finely-divided  particles  of  crystals  and 
glass  would  be  easily  attacked,  sulphates  and  chlorides  of  lime,  magnesia,  iron,  and 
the  alkalies  being  formed.  All  these  substances  were  found  in  greater  or  less 
abundance  in  the  specimens  of  dust  from  various  localities. 

Concerning  the  quantity  of  dust  thrown  into  the  air  during  the  Krakatoa 
eruptions,  we  have  no  data  for  forming  any  trustworthy  estimate.  The  continuance 
for  more  than  three  months  of  the  work  of  trituration  among  the  masses  of  pumice, 
of  so  particularly  brittle  a  character  as  that  ejected  from  Krakatoa,  must  have 
given  rise  to  a  large  quantity  of  tine  particles  which  would  be  gradually  diffused  in 
the  higher  regions  of  the  atmosphere.  The  last  violent  outburst,  however,  was  of  but 
short  duration,  and  the  area  over  which  the  dust-cloud  spread,  and  the  time  during 
which  darkness  prevailed,  were  small  as  compared  with  the  area  and  duration  of  the 
dust-cloud  during  the  Tomboro  and  some  other  great  eruptions. 

On  the  other  hand,  it  may  be  remarked  that  there  is  i-eason  for  believing  that 
the  last  paroxysmal  discharges  from  Krakatoa  were  of  altogether  exceptional  violence, 
and  that  water-  and  lava-dust  may  have  been  forcibly  carried  into  those  higher 
atmospheric  strata  which  are  characterised  by  extreme  rarefaction  and  great  electrical 
repulsion — strata  into  which,  in  ordinary  circumstances,  such  particles  have  no  chance 
of  finding  their  way. 

What  was  the  percentage  of  ultra-microscopical  particles  which  remained  in  the 

atmosphere  afber  the  larger  ones  had  fallen  it  is  impossible  to  determine^  but  it  waa 

not  improbably  very  considerable.      It  is  for  physicists  to  determine  whether  such 

particles  were  capable  of  producing  the  wonderful  optical  phenomena  which  followed 

G 


42  PROP.  JUDD   ON   THE   VOLCANIC   PHENOMENA. 

the  eruption  of  Krakatoa,  either  acting  by  themselves,  or  performing  the  part  of 
condensers  of  watery  vapour,  in  the  manner  which  Mr.  Ajtken  has  shown  such 
particles  to  be  capable  of  doing. 

A  question  which  has  often  been  asked  is  : — If  the  optical  phenomena  in  question 
resulted  from  the  presence  of  fine  particles  floating  in  the  atmosphere,  might  not 
these  be  carried  down  by  rain  and  detected  after  they  had  fallen  ?  I  am  indebted  to 
a  very  large  number  of  correspondents,  who,  ever  since  the  great  eruption,  have  been 
sending  to  me  specimens  of  dust,  of  materials  scraped  fi*om  freshly  fallen  snow,  and 
the  sediments  found  in  rain-gauges.  But  although  the  study  of  these  was  very 
interesting  in  itself,  yet  as  far  as  aiding  to  establish  the  presence  of  the  Exakatoa- 
dust  in  the  atmosphere  went,  the  results  have  been  altogether  negative. 

Nor  is  this  result  different  from  what  might  have  been  anticipated,  as  a  little 
consideration  will  serve  to  show.  The  most  characteristic  substance  in  the  Erakatoa 
dust  is  the  rhombic  pyroxene  (enstatite).  But  this  is  one  of  the  substances  which,  from 
its  high  specific  gravity  and  its  slight  friability,  woidd  be  among  the  first  to  fall. 
Moreover,  this  mineral  occurs  much  more  widely  than  was  at  one  time  supposed, 
being  found  very  commonly  in  many  of  the  andesites,  which  are  the  most  widely 
diffused  of  all  lavas,  except  perhaps  the  basalts. 

None  but  those  who  have  had  occasion  to  study  the  matter  for  themselves  can 
have  any  idea  of  the  quantity  of  mineral  particles  which  are  everywhere  floating 
about  in  the  atmosphere  ;  but  those  of  local  origin  of  course  usually  largely  predomi- 
nate, and  serve  to  mask  the  particles  which  have  come  from  great  distances.  If  the 
optical  phenomena  which  followed  the  eruption  of  Ki*akatoa  are  rightly  regarded  as 
being  due  to  dust  in  the  atmosphere,  they  would  probably  result  from  the  action  of 
ultra- microscopical  particles,  for  it  is  these,  which,  by  scattering  light,  have  the  power 
of  producing  colour-effects.  Such  particles  it  is  of  course  hopeless  to  attempt  to  seek 
for  in  the  manner  described. 


General  CoNOiiUSiONS. 

The  thoughtful  consideration  of  some  of  the  facts  which  have  been  detailed  in  the 
foregoing  paragraphs  is  calculated,  I  believe,  to  afford  an  important  insight  into  the 
nature  of  the  forces  which  give  rise  to  volcanic  outbursts,  and  to  the  causes  of 
the  variation  in  character  of  these  phenomena,  in  different  places  and  at  various 
times. 

All  the  materials  ejected  from  the  central  vent  of  Krakatoa  have  been  wonder- 
fully similar  in  their  chemical  and  mineralogical  constitution.  At  one  period  of  the 
volcano's  history,  it  is  true,  basaltic  lavas  and  tuffs  were  thrown  out  from  a  lateral 
vent,  and  of  these  the  parasitical  cone  of  Rakata  is  built  up  ;  but  both  before  and  since 
this  episode  in  the  history  of  Erakatoa,  the  materials  ejected  from  the  central  crater 


PROF.  JUDD   ON   THE  VOLCANIC    PHENOMENA. 


43 


have  always  belonged  to  the  remarkable  class  of  enstatite-dacite  rocks.    The  composition 
of  these  rocks  may  be  represented  by  the  following  general  averages  :— 


Silica  (with  Titanic  Acid) 
Alumina  . . 
Oxides  of  Iron    .  • 
Lime  and  Magnesia 
Potash      , . 
Soda 


70 

15 
4 
5 

2 


Total 


..    100 


In  this  magma  apparently,  by  a  first  consolidation,  well-developed  crystals,  equal 
to  about  10  per  cent,  of  the  whole  mass,  seem  to  have  been  separated,  these  crystals 
consisting  of  6  per  cent,  of  felspar,  2  per  cent,  of  ferriferous  enstatite  and  augite  (the 
former  mineral*  being  twice  as  abundant  as  the  latter),  and  2  per  cent,  of  magnetite. 
Making  a  calculation  on  the  basis  of  the  composition  actually  found  by  analysis  for 
the  whole  rock,  and  the  several  minerals  present,  the  base  or  ground-mass  of  these 
rocks  would  have  the  following  composition  : — 


Silica  (with  Titanic  Acid) 

. .     72-8 

Alumina 

. .      147 

Oxides  of  Iron.. 

1-8 

Lime  and  Magnesia     . . 

4-4 

Potash 

2-2 

Soda 

4-1 

Total     .. 

..    lOO-O 

This  magma  exhibits  a  greater  or  less  degree  of  devitrification  iu  different  cases, 
microlites  of  felspar,  pyroxene,  and  magnetite  belonging  to  a  second  period  of 
consolidation,  separating  from  it  sometimes  in  small  quantities,  at  other  times  to 
such  an  extent  as  to  convert  the  glassy  base  into  a  stony  one. 

It  is  scarcely  possible  to  doubt  that  the  separation  of  the  larger  and  porphyritic 

ciystals  from  the  magma,  must  have  taken  place  under  totally  different  conditions 

from  those  of  the  second  consolidation  ;  in  all  probability,  when  the  mass  existed  at 

great  depth  and  under  intense  pressure.     And  it  is  by  no  means  certain  that  the 

proportion  of  glassy  matrix  to  the  included  minerals  has  not  been  altered  since  the 

crystallization  of  the  latter. 

02 


44  PEOP.  JUDD  ON  THE  VOLCANIC  PHENOMENA. 

Now  the  startling  fact  which  comes  into  prominence  when  the  lavas  of  the 
earlier  and  later  periods  of  eruptive  activity  at  Krakatoa  are  studied  in  the  field  is 
that,  in  spite  of  this  identity  in  chemical  composition  and  of  the  included  minerals, 
their  mode  of  behaviour  has  been  strikingly  dissimilar. 

During  the  earlier  period,  massive  lava-streams  flowed  firom  the  central  vent, 
almost  unaccompanied  by  any  explosive  action,  and  these  lavas  gradually  accumulated 
to  build  up  a  bulky  cone.  In  these  massive  lavas  the  slow  cooling  down  of  the 
molten  rock  permitted  of  the  imperfect  crystallization  of  the  felspar,  pyroxene,  and 
magnetite  from  the  base;  where  the  cooling  was  somewhat  rapid,  magnetite  and 
felspar  were  the  chief  minerals  formed,  as  in  the  pitchstones;  where  less  rapid, 
felspars  and  pyroxenes,  as  in  the  stony  lavas. 

But  during  the  later  period  a  lava  having  precisely  the  same  chemical  composition 
exhibited  perfect  liquidity.  Occasional  lava-streams  composed  of  this  material  are 
found,  as  at  Perboewatan,  but  the  greater  portion  of  it,  on  being  relieved  from 
pressure  by  coming  into  the  outer  atmosphere,  at  once  became  distended  into 
pumice,  through  the  escape  of  the  volatile  materials  imprisoned  in  its  midst. 

Now,  what  is  the  cause  of  the  diflFerence  of  behaviour  of  the  same  chemical 
compound  in  these  two  cases  ?  It  might,  at  first  sight,  appear  that  the  cause  of 
this  difference  is  to  be  sought  in  variations  of  temperature,  and  that  the  later  lavas 
were  more  liquid  because  at  a  higher  temperature,  and  more  thoroughly  fused  than  the 
earlier  ones. 

But  if  we  examine  the  porphyritic  crystals  of  the  same  minerals  which  have 
floated  about  in  the  magma  in  both  cases,  we  shall  find  that  all  the  evidence  points  to 
exactly  the  opposite  conclusion,  namely,  that  the  pitchstone-rock  was  actually  at  the 
higher  temperature,  for  the  crystals  of  felspar  in  the  obsidian-rock  are  often  almost 
uncorroded,  while  in  the  pitchstone  they  have  been  attacked  by  the  fluid  in  which 
they  floated,  and  have  indeed  been  to  a  great  extent  dissolved  by  it. 

If  we  now  try  the  actual  fiisibilities  of  the  magmas  in  the  two  cases,  we  shall 
find  the  inference  derived  from  the  condition  of  the  felspar-crystals  to  be  strikingly 
confirmed.  In  the  case  of  the  pitchstone,  portions  of  the  substance  held  in  the  flame 
of  a  jet  urged  by  a  strong  blast  are  hardly  affected,  while  in  the  case  of  the  obsidian 
the  material  under  the  same  conditions  rapidly  becomes  liquid. 

But  this  production  of  liquidity  in  the  obsidian  is  attended  with  the  disengage- 
ment of  a  large  quantity  of  volatile  materials  by  which  the  rock  rapidly  passes  into 
the  condition  of  a  pumice.  It  is,  therefore,  impossible  to  avoid  connecting  the  presence 
of  these  volatile  matters  in  the  rock  with  the  production  of  its  liquidity. 

I  have  in  another  place  *  pointed  out  that  the  leucite-basalts  of  similar  com- 
position ejected  from  Vesuvius  at  different  periods  exhibit  just  the  same  differences. 
When,  as  in  the  lavas  of  1872,  the  quantity  of  steam  and  gas  ^ven  off  from  them 

•  See  *  Geol  Mag-.,'  Dec.  li.,  vol.  ii.  (1875),  p.  68  ;  also  •  Volcwioes,'  p.  92. 


PROP.  JUDD  ON   THE  VOLCANIC   PHENOMENA.  45 

was  large,  their  liquidity  was  perfect;  when,  as  in  1858,  the  quantity  of  volatile 
matter  was  small,  the  lavas  exhibited  the  greatest  viscosity. 

That  by  admixture  with  varying  quantities  of  water  many  salts  have  their 
fusion-points  proportionately  reduced  has  long  been  known.  Indeed,  the  late  Dr. 
GuTHME,  F.R.S.,  by  his  interesting  experiments  upon  nitre,  was  able  to  demonstrate 
that  there  is  actual  continuity  between  the  two  states  of  fluidity  known  by  the  names 
of  solution  and  fusion  respectively.  For,  as  there  is  a  perfectly  gradual  rise  in  the 
temperature  at  which  liquidity  is  produced  when  more  and  more  nitre  is  added  to  a 
definite  quantity  of  water,  it  becomes  impossible  to  decide  when  the  proportion  of  the 
water  becomes  so  small  that  we  can  no  longer  regard  the  case  as  one  of  "  solution," 
and  we  must  begin  to  call  it  "  fusion.''* 

That  the  silicates,  like  other  salts,  have  their  fusion-points  lowered  by  admixture 
with  water,  we  have  many  proofs.  Most  of  the  felspars  are  minerals  of  difficult 
fusibility,  while  the  zeolites,  which  are  analogous  compounds  of  the  silicates  of 
alumina  and  the  silicates  of  potash,  soda,  and  lime,  with  the  addition  of  water,  are 
remarkable  for  their  easy  fiisibility  and  for  the  manner  in  which  they  swell  up  and 
lose  their  waters  at  a  comparatively  low  temperature.  And  this  is  true,  not  only 
of  definite  hydrous  silicates,  like  the  zeolites;  the  colloids  of  indefinite  chemical 
composition,  such  as  tachylyte,  hydrotachylyte,  and  palagonite,  appear,  to  have  their 
fusion-points  lowered  according  to  the  proportion  of  water  that  they  contain. 

In  the  case  of  the  Krakatoa-lavas  we  have  the  clearest  evidence  that  when  the 
mixtures  of  silicates  of  which  they  consist  contain  water,  then  very  fusible  glasses 
are  formed.  In  these  circumstances,  the  earlier  formed  porphyritic  crystals  are 
but  little  hable  to  be  attacked  by  the  liquid  magma  in  which  they  float.  As  the 
interesting  synthetic  researches  of  MM.  Fougu^  and  L^VY  have  shown  that  any 
particular  mineral  is  liable  to  separate  from  a  magma  when  the  latter  is  kept  for  a 
long  time  at  a  temperature  just  below  the  point  of  fusion  of  the  mineral,  we  can 
understand  how  small  is  the  chance  of  devitrification  taking  place  in  magmas  which 
are  liquified  at  low  temperatures,  and  which,  by  a  small  reduction  of  temperature, 
become  solid. 

In  other  magmas,  however,  consisting  of  precisely  the  same  admixture  of  sili- 
cates, but  without  water,  we  find  the  fusion-point  far  higher.  The  excessively  heated 
magma  in  such  cases  exercises  the  strongest  solvent  action  on  the  crystals  of  felspar 
immersed  in  it ;  and  in  cooling  down,  much  magnetite,  augite,  enstatite,  and  felspar 
separate  out  from  it  before  it  solidifies. 

I  am  convinced  that  this  is  a  class  of  questions  to  which  petrologists  will  have 
to  give  much  greater  attention  than  they  have  hitherto  done.  The  characters 
assumed  by  an  igneous  rock  depend  not  only  on  the  peculiar  admixture  of  silicates 
which  compose  it,  but  also  on  the  temperature  at  which  liquefaction  and  solidification 

♦  *  Phil.  Mag.,'  vol.  xviii.  (1884),  p.  22. 


46  PROP.  JUDD   ON  THE  VOLCANIC  PHENOMENA. 

could  take  place  in  the  mass;  this  being  to  a  great  extent  dependent  on  the  quantity 
of  water  that  was  present.  The  temperature  at  which  fusion  could  take  place  would 
largely  determine  not  only  the  minerals  which  separated  out  from  the  magma,  but 
also  the  degree  and  nature  of  their  crystallization.  In  other  words,  the  texture  as 
well  as  the  mineralogical  constitution  of  the  rock  would  be  greatly  influenced  by  the 
proportion  of  water  present  in  the  magma  from  which  it  was  formed. 

In  the  same  way  the  actual  nature  of  the  volcanic  manifestations  at  any 
particular  vent  are  seen  to  be  determined,  not  so  much  by  the  mineralogical 
constitution  of  the  lava,  as  by  the  circiunstance  of  the  quantity  of  water  contained 
in  the  magma.  Where  this  is  great,  the  lava  will  be  perfectly  liquid,  and  will  be 
almost  wholly  thrown  out  in  the  form  of  pumice  and  dust.  On  the  other  hand,  lavas 
containing  little  water  will  require  a  very  high  temperature  for  their  Aision,  and  they 
wlQ  be  characterised  by  great  viscosity  rather  than  perfect  liquidity. 

If,  as  seems  highly  probable,  the  younger  ejecta  of  Krakatoa  were  formed  by  the 
re-fusion  of  the  older  lavas,  then  we  can  trace  the  cause  of  the  introduction  of  water 
by  which  their  liquefaction  by  heat  was  rendered  more  easy.  These  older  lavas,  by 
the  presence  in  them  of  hydrous  compounds,  and  by  the  existence  in  their  cavities  of 
tridymite  and  other  secondary  minerals,  betray  the  fact  that  they  have  been  greatly 
acted  upon  by  percolating  waters.  It  is  through  the  introduction  of  the  sea  and 
other  surface-waters  into  rock-masses  by  slow  percolation  from  above,  and  the 
consequent  formation  of  new  compounds,  more  readily  acted  upon  by  subterranean 
heat,  that  I  am  disposed  to  regard  volcanic  phenomena  as  being  brought  about.  In 
this  we  find  an  explanation  of  the  proximity  of  volcanoes  to  great  bodies  of  water, 
which  it  seems  to  me  is  far  more  in  accord  with  the  actual  phenomena  than  the 
supposition  that  water  finds  access  to  volcanic  foci  by  means  of  actual  open  fissures. 


NoTR. — It  is  very  greatly  to  be  regretted  that  no  accurate  survey  of  Krakatoa,  and  of  the  sarronnding 
seas  was  made  prior  to  the  great  eruption  of  1883.  Had  such  been  done,  a  splendid  opportunity  would 
have  been  afforded  us  for  determining  whether  elevation  and  sabsequent  subsidence  of  the  whole  mass 
of  the  volcano  actually  occurred.  The  existing  statements  concerning  the  height  of  the  peak  of  Bakata 
before  and  after  the  eruption  are  so  confused  and  contradictory  (see  p.  23  and  foot-note),  while  both  the 
outlines  and  soundings  on  the  old  charts  appear  to  be  so  untrustworthy,  that  I  fail  to  detect  certain 
evidence  of  any  movements  of  the  kind.  As  the  phenomena  observed  at  Krakatoa  seem  to  be  reconcil- 
able with  principles  already  well  established  by  the  study  of  other  volcanoes,  I  have  felt  it  incumbent 
on  me  to  adopt  such  interpretations  in  preference  to  those  which  depend  on  movements  of  the  volcanic 
mass  which  are  of  a  conjectural  character. 

The  theoretical  questions,  suggested  by  the  study  of  the  Kitikatoa-lavas,  have  been  more  fully 
discupsed  by  the  author  in  a  paper  read  before  the  Geological  Section  of  the  British  Association  at  tlie 
meeting  in  Manchester  in  1887.  The  paper  is  published  in  the  '  Geological  Magazine,'  Dec.  iii.,  vol.  t. 
(1888),  p.  1. 

J.  W.  JUDD. 


MR.  R.  H.   SCOTT   ON   THE   PUMICE.  47 

APPENDIX. 


Meteorological  Officey 

116,  Victoria  Street,  LoiidoUy  S.W. 

Memorandum. 

I  have  examined  the  various  statements  as  to  the  meeting  of  pumice  in  the 
Indian  Ocean  in  the  course  of  the  years  1883  and  1884. 

With  the  exception  of  the  masses  of  floating  pumice,  often  bearing  uprooted 
trees,  &c.,  vehich  blocked  the  Strait  of  Sunda  and  the  adjacent  harbours  of  Java 
and  Sumatra,  the  great  majority  of  entries  of  the  substance  come  from  the  region 
reaching  in  latitude  from  the  Equator  to  20°  S.,  and  in  longitude  from  70°  to  100°  E. 

One  observer.  Captain  Reeves,  of  the  barque  Umvoti,  speaks  of  two  masses — 
one  between  20°  and  25°  S.,  the  other  between  10°  and  5°  S.  These  are  separated 
by  an  interval  of  clear  sea. 

Furthermore,  a  coasting  vessel  which  arrived  at  Sydney,  August  4,  1884,  from 
a  vQyage  round  Australia,  reported  that  *'  all  along  the  north  and  west  coasts  of  the 
continent  vast  shoals  of  pumice  were  passed  through,"  This  was  probably  in  June 
or  July,  1884. 

As  the  observers  almost  without  exception  found  the  pumice  thickly  coated  with 
barnacles  {Lepa^  ansi/era,  the  common  southern  species),  the  material  must  have  been 
a  long  time  in  the  water. 

We  know  that  Krakatoa  was  in  eruption  in  May,  1883,  and  continued  more  or 
less  active  for  three  months,  and  as  pumice  was  met  with  by  H.M.S.  Magpie  in 
6°  S.  and  61°  E.,  April  22,  1884,  it  seems  impracticable  to  trace  the  course  of  any 
particular  deposits  of  this  material  on  the  sea  surface. 

It  is,  however,  interesting  to  learn  that  the  precise  dates  of  the  arrival  of  pumice 
on  the  coasts  of  Natal,  and  on  the  Chagos  Islands,  were  as  follows  : — 

Natal,  September  27th  and  28th,  1884. 
Diego  Garcia  (Chagos),  October  1st,  1884. 

As  Diego  Garcia  is  in  7°  S.  and  73°  E.  (approximately),  while  Durban  is  in 
30^  S.  and  31°  E.,  it  is  not  likely  that  the  pumice  which  reached  these  two  distant 
stations  nearly  simultaneously  could  have  been  ejected  at  the  same  time. 

In  all  discussions  of  the  movements  of  the  pumice  it  must  be  remembered  that 
floating  bodies  will  be  much  affected  by  the  wind,  and  wiU  not  drift  solely  in  accord- 
ance with  ocean  currents. 

The  deposits  of  pumice  near  the  coast  of  Australia  may  have  drifted  there  before 

the  north-west  monsoon,  which  would  prevail  in  those  seas  from  November,  1883,  to 

March,  1884. 

EOBEET  H.  SCOTT. 


48 


DR.  MBLDRUM  ON  THE   PUMIOE  AND  VOLCANIC   DUST. 


A  Tah\dar  Statement  of  the  Dates  on  which,  and  the  Localities  where,  Pumice  or 
Volcanic  Dust  was  seen  in  the  Indian  Ocean  in  1883-84.  By  Charles 
Meldrum,  LL,D.,  F.RS. 

(Reprinted,  by  peionission,  from  the  '  British  Association  Report/  1885,  p.  773.) 


Names  of  Vessels. 


Barque  Actcsa   (Capt. 
Walker) 


Ship    Idomene   (Capt. 
Johnson) 

Barqne    West  Auttra- 
lian  (Capt.  Thomas) 


S.S.    Anerley    (Capt. 
Strachan) 


Barque  County  of  Flint 
(Capt.  J.  Rowland) 


French     brig     Brani 
(Capt.  E.  Perrot) 


Day  of 
Year. 


140 

141 
141 


229 


230 


231 


239 


240 


240 


240 


Month 
and 
Day. 


1883 
May      20 

n  21 

n  21 


Aug.  11 

„  17 

„  18 

„  19 

M    .  27 

„  28 

„  28 

„  28 


Hours. 


Position 
at  Noon. 


Lat. 


2  p.m. 

to 
9  a.m. 
night 


8  a.m.  to 
2  p.m. 


noon 


noon 


noon 


6  50  8. 


6  23  S. 
noon  8  35  S. 


9  41  S. 


11  08  S. 


Long. 


E. 

101  02 


88  31 
91  53 

90  28 
88  03 


North  Watcher 


Anjer  Roads 


8  20  S. 


4  22  S. 


92    04 


91    34 


Remarks. 


Very  fine  dust  commenced 
to  fall  about  2  p.m. 
The  fall  continued  all 
night,  and  stopped  about 
9  a.m.  on  the  21st. 
Small  quantities  fell 
again  during  the  night. 

Passed  through  large  fields 
.of  pumice. 

Passed  a  great  amount  of 
floating  lava  or  pumice. 

Passed  a  great  amount  of 
lava  to-day. 

Large  quantities  of  pumice ; 
some  pieces  about  3  feet 
in  diameter. 

Ashes  began  to  fall  at 
10.24  a.m.  Showers  of 
ashes  and  pumice  lasted 
till  midnight. 

Immense  quantities  of 
pumice  and  debris  of 
all  sorts. 

Great  quantity  of  dust 
falling ;  supposed  to  be 
coral  dust. 

L'atmosph^re  surcharge  de 
sable.  De  minuit  ^11 
heures  du  matin  une 
tr^s  grande  quantity  de 
sable  tr^  blanc  et  tree 
fin  a  courert  toutes  les 
parties  accessibles,  m^me 
presque  dans  la  chambre. 
Je  crois  que  c'est  le 
resultat  d'un  orage  que 


DR.   MELDRUM   ON  THE   PUMICE  AND  VOLCANIC   DUST. 


49 


Names  of  Vessels. 

Day  of 
Year. 

Month 
and 
Day. 

Hours. 

Position 
at  Noon. 

Remarks. 

Lat. 

Long. 

1883 

E. 

f^rench  brig    Brani — 
contmned. 

•     1 

O         i 

nous  avions  observe  ceg 
jours  derniei*s  sur  Su- 
matra, pendant  lequel 
le  tonnerre  avait  des 
roulements  pareils  k  une 
canonnade,  et  le  sable 
enlev^  par  cette  tour- 
mente  a  ^t6  renvoy^  sap 
nous  par  la  petite  brise. 

241 

Aug.      29 

9a.in. 

5  50  S.  '      91  20 

! 
1 

II  tombe  continuellement 
du  sable  tr^  fin  au 
point  d*obscurcir  ratmos- 
ph^re. 

Barque    Catileton 
(Capt.  Dior6) 

240 

„         28 

2  a.m. 

5  58  S. 

1      93  30 

After  a  shower  of  rain  the 
air  became  loaded  with 
a  fine  dust,  which  fell 
in  great  quantities  on 
deck.  At  noon  dust  still 
failing.  At  2  p.m.  dust 
still  falling. 

• 

241 

,,         29 

6  a.m. 
2  p.m. 

6  66  S. 

93  01 

Collected  dust  off  the  deck. 
Pumice-stone  floating  in 
the  water.  At  2  p.m. 
dnst  still  falling :  large 
quantities  of  pumice 
floating  past. 

Brigantme    Airlie 
(Capt.  Knight) 

252 

Sept.       9 

6  a.m. 
2  p.m. 

7  31  S. 

103  11 

Large  quantities  of  lava. 
Passing  through  large 
quantities  of  lava. 

French    barqne  Qipsy 
(Capt.  Martin) 

252 

9 

9  a.m. 

4  57  S. 

82  06 

Grand  banc  flottant  de 
pierre-poDce  pendant 
toute  la  journee,  suivant 
le  Tent  comme  dans  la 
mer  de  Sargosse. 

Frencli  barque  Marie 
Alfred  (Capt.   Br6. 
geon) 

263 

,.         20 

6  a.m. 

7  02  S. 

101  15 

Noas  passons  dans  des 
bancs  succcssifs  et  tr^s 
rapproch^s  de  pierre- 
ponce. 

Barqne  Hottenhura 
(Capt.  Chichester) 

286 

Oct.       IS 

4  p.m. 

Snnda 

Strait 

Tremendous  fields  of  pum- 
ice stopped  the  yessel. 

287 

„         14 

4  a.m. 

No 

obs. 

Lots  of  pumice  alongside. 

288 

„         15 

midt. 

7  19  S. 

104  00 

Passing  large  fields  of 
pumice. 

50 


DR.  MELDRUM  ON   THE   PUMICE   AND  VOLCANIC   DUST. 


Namea  of  Yesgels. 


Day  of 
Year. 


Month 
and 
Day. 


Honrs. 


Position 
at  Noon. 


Lat. 


Long. 


Bemarlca. 


S.S.  Oaronne 


LS.  Countess  of  Errol 
(Capt.  Taylor) 


Barqne    Bollo    (Capt. 
CuiTie) 


Barqne     lEva     Joshua 
(Capt.  Florentin) 


Fiencli  barqne  Hen- 
riette  (Capt.  A.  de 
Lavit) 


Barqne  Ta  Lee  (Capt. 
Stolzee) 


294 


299 


300 


319 


320 

321 
332 

336 


337 

338 

339 


341 


1883 

Oct. 

21 

916 
a.m. 

»» 

26 

noon 

n 

27 

8a.ni. 

Nov. 

16 

6  a.m. 

»1 

16 

noon 

»» 

17 

noon 

)> 

28 

8  a.m. 

Dec- 

2 

6  a.m. 

»f 

3 

6  a.m. 

)> 

4 

6  a.m. 

9> 

5 

9  a.m. 

»» 

2 

4  p.m. 

)9 

7 

a.m. 

l5  15  s. 


E. 

o        / 

78  07 


7  01  S. 

8  44S. 
6  19  S. 

8  04  S. 

9  36  S. 
6  24  S. 

6  42  S. 


104  49 
102  40 

88  66 

87  26 

86  46 
64  46 

89  07 


No 

7  14  S. 

8  44S. 
6  07  S. 

8  69  S. 


oba. 


87  32 

? 

81  66 

82  14 


Passed  throngh  aeyend 
fields  of  pnmice-stone  of 
varions  sizes.  Some 
pieces  that  were  picked 
np  had  barnacles  nearly 
one  inch  long  adhering 
to  them. 

Vast  qnantities  of  pnmice 
all  ronnd  the  ship. 

Sailing  throngh  vast  qnan- 
tities of  pnmice. 

Since  daylight  sailing 
throngh  large  qnantities 
of  pnmice.  At  midnight 
still  lai^e  qnantities  of 
pum  ice  floating  on  water. 

Still  large  qnantities  of 
pnmice  floating  past. 


Sailing  all  day  throngh 
floating  pnmice  covered 
with  barnacles. 

An  jonr  nons  avons  re- 
marqn^  qne  noas  ^Uona 
environues  de  pterre- 
ponce.  A  9  henres  nons 
sommes  tonjonrs  enton- 
r^s  de  pieire-pouoe. 

II  y  a  encore  de  pierre-ponce. 

Nons  avons  encore  ren- 
contre de  pierre-ponce. 

Nons  recontrons  encore 
beanconp  de  pierre- 
ponce. 

Passed  a  bank  of  pnmloe 
extending  abont  twenty- 
five  miles  ;  some  pieces 
abont  two  feet  square. 

Still  passing  p  amice-stone 
and  a  kind  of  ashes. 


DR.  MBLDRUM  ON   THE  PUMICE   AND  VOLCANIC   DUST. 


51 


Names  of  Vessels. 


Day 

of 

Year. 


Month 
and 
Day. 


Hours. 


Position  at 
Noon. 


Lat 


Long. 


Remarks. 


8hip    Shah  Jehan 
(Capt.  Williams) 


Ship  Ifwereauld  (Capt. 
Leslie) 


Barque  Evelyn  (Capt. 
Stevenson) 


Barque     May     Queen 
(Capt.  Hngon) 


Sch.      Lord    Tredegar 
(Capt.  Clarke) 


343 


84.7 


348 


349 


346 


348 


349 


354 


355 


362 


8 
9 

10 


1883 
Deo.        9 


6  a.m. 


18 


14 


15 


12 


14 


15 


20 


21 


28 


1884 
Jan.         5 


8 
9 

10 


8  a.m. 


10  a.m. 


noon 


2  p.m. 


noon 


noon 


^  26  S. 


13  47  s: 


15  03  & 


15  80  S. 


11  45  S. 


9  54  8. 


a.m.  7  56  i 


9  40  S. 
7  30  S. 
2  14  N. 

6  35  S. 

12  12  S. 
14  56  S. 

17  34  S. 


E. 


M  58 


82  00 

81  42 

80  51 

87  09 

87  56 
89  32 

88  11 
88  26 
85  35 

68  25 

66  59 
65  18 

63  04- 


Noticed  the  sea  ooyered 
in  streaks  with  what 
appeared  to  be  pnmice- 
stone  in  pieces  and  iu 
powder ;  lowered  the 
boat  and  picked  up  some ; 
some  of  the  stones 
covered  with  barnacles. 

Throughout  the  day  the 
sea  covered  in  streaks 
with  some  kind  of  lava 
and  ]arg8-sized  lumps  of 
pumice-stone. 

Passed  a  great  deal  of 
pumice  and  lava  this 
day. 

Passed  a  lot  of  pumice  and 
lava. 

Passed  through  a  quantity 
of  dnst  seemingly  floating 
on  the  surface. 

Passed  through  a  quantify 
of  pumice-stone. 

Passed  large  quantities  of 
pumice-stone. 

Passing  great  quantities  of 
pumice. 

Still  passing  quantities  of 
pumice. 

Une  infinite  de  parcelles 
de  roche  brdlee  sur  Teau. 


Passed  throngh  a  quantity 
of  lava. 


Passed  throngh  a  great 
quantity  of  pnmice  to- 
day. 


H  2 


52 


DR.  MELDRUM  ON  THE  PUMICE  AND   VOLCANIC   DUST. 


Names  of  Vessels. 

Tear. 

Month 
and 
Day. 

Hoars. 

Position  at 
Noon. 

Bemarka. 

Lat. 

Long. 

1884 

E. 

French  barque  Besolu 
(Capt.  Monton) 

8 

Jan. 

8 

p.m. 

?  06  S. 

.MOi 

Trayers^  plosienrs  bancs 
de  pieire-ponce. 

Barqae  May  Queen 
(Capt.  Hagon) 

9 

Y> 

9 

a.m. 

7  COS. 

83  13 

Une  infinite  de  roche  br6l^ 
flottant. 

12 

»> 

12 

p.m. 

11  23  S. 

75  46 

Une  infinite  de  debris  voU 
caniques. 

Ship  Argomene' (C9,pt. 
H.  Williams) 

12 

»9 

12 

8  p.m. 

7  51  S. 

87  06 

Fusing  through  large 
quantities  of  pumice. 

Ship  Boderick  DM 
(Capt.  Boldchild) 

13 

11 

13 

4  p.m. 

13  34  S. 

90  j;0 

Passing  through  large 
quantities  of  pumice. 

14 

»» 

14 

p.m. 

9  25  S. 

90  26 

>i             «             » 

French  barqae  Eugenie 
(Capt.  A.  Amaad) 

15 

»> 

15 

p.m. 

6  14  S. 

81  40 

Beaucoup  de  pierre-ponce 
formant  de  lis  allong6  a 
Touest. 

Barqne  Star  of  Greece 
(Capt.  W.  Legg) 

21 

»> 

21 

7  a.m. 

18  49  S. 

85  45 

Tjarge  quantities  of  pumice 
in  separate  streams  from 
S.E.  toN.W.  At  6  p.m. 
still  passing  large  quan* 
tities  of  pumice. 

22 

i» 

22 

2  a.m. 

13  21  S. 

86  06 

The  streams  of  pumice- 
stone  stopped* 

23 

n 

23 

midt. 

10  45  S. 

86  60 

A  large  stream  of  pumice- 
stone. 

Barque  Eva  Joshua 
(Capt.  Florentin) 

22 

>» 

22 

p.m. 

13  05  S. 

66  40 

Sighted  pumice-stone. 

Sch.     aienesk    (Capt. 
Feleng) 

26 

»f 

26 

a.m. 

3  19  S. 

81  05 

Benoontr^  &  chaque  instant 
des  bancs  form6s  par 
des  pierres-ponoe. 

Sch.    Mary   Whitridge 
(Capt.  Howfts) 

40 

Feb. 

9 

7  a.m. 

9  41  S. 

88  26 

Passing    lots    of    floating* 
pumice-stone. 

41 

>1 

10 

5  a.m. 

8  lis. 

89  24 

n                    )>                   9* 

42 

»> 

11 

5  a.m. 

5  06S. 

90  11 

»                    »>                    »J 

43 

>» 

12 

2  a.m. 

2  43S. 

91  26 

Passing    large    fields     of 
pumice. 

DR.  MELDBUM   ON   THE  PUMICE  AND   VOLCANIC   DUST. 


53 


Names,  of  Vessels. 

Day 

of 

Tear. 

Month 
and 
Day. 

Honrs. 

Position  at 
Noon, 

Reouirks. 

Lat. 

Long. 

1884 

B. 

Barqne  County  of  Flint 
(Capt.  J.  Rowland) 

57 

Feb.      26 

— 

i  27  S. 

86  63 

Great  quantities  of  pumice, 
which  appears  to  have 
been  long  in  the  water. 

58 

„        27 

— 

1  SOS. 

87  48 

Pumice-stone  passing. 

61 

March     1 

4  a.m. 

2  21  S. 

86  21 

Great  quantities  of  pumice- 
stone  in  sight. 

62 

2 

2  a.m. 

2  40  S. 

84  31 

Great  quantities  of  pumice 
passing. 

63 

„          3  1  2  p.m. 

1 

2  36  S. 

84  10 

»           »>           »> 

65 

„          5     3  a.m. 

4  01  S. 

83  57 

»           »>          >» 

} 

2  p.m. 

— 

— 

)'           »»           jt 

Ship  FaHhenope  (Capt. 
F.Gray) 

64 

4 

— 

1  36  S. 

87  21 

Sea  strewed  with  pumice* 
stone  covered  with 
barnacles. 

65 

5 

— 

2  14  S. 

87  21 

>i           >»           » 

. 

66 

6 

— 

3  36  S. 

88  04 

9J                      7)                      >f 

70 

„        10 

— 

5  52  S. 

88  16 

>>                       >9                       )f 

72 

,,         12 

— 

10  38  S. 

86  09 

Sea  covered  with  lava  and 
pumice  2  feet  thick. 

75 

„         15 

— 

17  49  S. 

70  40 

Sea  strewed  with  lava  and 
pumice. 

Ship  Kelvinside  (Capt. 

69 

9 

noon 

14  40  S. 

81  56 

Since  7th  been  sailing 
through  floating  pumice 
in  pieces  from  the  size 
of  a  cocoanut  to  pieces 
almost  like  dust. 

Barque  Excelsior 
(Capt  F.  Fidgar) 

72 

„        12 

6  p.m. 

20  27  S. 

78  09 

Great  quantities  of  floating 
pumice. 

Sch.  Iris  (Capt.  Shaw) 

82 

M        22 

p.m. 

9  35  S. 

76  39 

Passing  vast  quantities  of 
pumice. 

85 

„        25 

a.m. 

16  33  S. 

72  11 

>»                        5»                        « 

Sch.  Northern  Bell 
(Capt.  L.  Moiris) 

84 

,,        24 

p.m. 

26  33  S. 

70  00 

For  four  hours  passing  a 
vast  quantity  of  pumice- 
stone  covered  with 
barnacles. 

54 


DR.  MELDEUM  ON  THE  PUMICE  AND  VOLCANIC  DUST. 


Namefrof  Vessels. 

Tear. 

Month 
and 
Day. 

Hours. 

1 
Position  at 
Noon.               ( 

1 

RemarkB. 

Lat. 

Long. 

1884 

B. 

Ship  Inverccmld  (Gapi. 
Leslie) 

93 

April 

2 

a.n]. 

(K>  06  S. 

*3b 

Passing  through  aquantilTf 
of  pumioe. 

97 

)i 

6 

4  40S. 

91  13 

During  last  five  days  passed 
through  a  quantity  of 
pumice  -  stone,  of  a 
greenish  colour  and 
covered  with  barnacles 
and  crabs. 

Barqne  Evelyn  (Capt. 
Stevenson) 

102 

)> 

11 

a.m. 

2  10  S. 

90  13 

Passing  quantities  of 
pnmioe-stone. 

Barque    Peggie    Boy 
(Capt.  Hill) 

106 

i» 

15 

a.m. 

11  34  S. 

69  02 

Passed  large  quantities  of 
pumice. 

112 

11 

21 

a.m. 

16  65  S. 

68  22 

Passed  quantities  of 
pumice. 

S.8.  Madagasear  (Capt. 
A.  Vielle) 

120 

)i 

29 

p.m. 

18  22  S. 

67  16 

Several  pieces  of  pumice 
floating  alongside. 

Ship      Knight     Com- 
mander (Capt.  BeU) 

120 

11 

29 

a.m. 

16  38  S. 

72  19 

Passed  through  fields 
of  pumice-stone  and 
scori». 

Barque  Caller  Ou 
(Capt.  Rae) 

125 

May 

4 

a.m. 

11  07  S. 

62  41 

Sailing  through  quantities 
of  lava. 

Lug^r  Success  (Capt. 
Hazel) 

125 

»» 

4 

10  16  S. 

62  35 

Depuis  plusieurs  jours  la 
mer  est  couverte  de 
pierre  et  de  sable  vol- 
canique  d*une  couleur 
jaun&tre. 

Ship     Knight      Com- 
panion (Capt.  Davis) 

136 

»t 

15 

a.m. 

10  32  S. 

88  53 

Passing  through  quantities 
of  pumice. 

Barque     Tris     (Capt. 
Evans) 

145 

»» 

24 

p.m. 

5  21  S. 

94  44 

A  great  quantity  of  floating 
pumice. 

French  barque  Louise 
Collet  (Capt.  Beck- 
man) 

152 

>» 

31 

a.m. 

12  43  S. 

81  29 

On  rencontre  tonjours  des 
pierres-pouce. 

Brig      Flora      (Capt. 
Menton) 

152 

1> 

31 

p.m. 

10  18  S. 

68  09 

Le  capitaine  tombe  a  la  mer 
en  p^chant  des  pierres- 
ponce. 

•Ship  Broomhall  (Capt. 
Grieve) 

165 

June 

13 

2  p.m. 

5  29  S. 

89  39 

Passing  through  quantities 
of  pumice  covered  with 
barnacles. 

DR.  MELDRUM  ON   THE   PUMICE  AND  VOLCANIC   DUST. 


55 


Names  of  Yessels. 


Drj 

of 

Year. 


MoDtH 
and 
Day. 


Hours. 


Position  at 
Noon. 


Lat. 


Long. 


Remarks. 


Brig  Bio  Loge  (Capt. 
Ix>yett) 


Sch.  Iris  (Capt.  Shaw) 


Ship    Beigate    (Capt. 
Ritchie) 


Barque  Northern  Btaa- 
(Capt.  Evans) 


Barqae  Ciiy  of  Tetnjore 
(Capt.  Sinclair) 


169 

169 
175 
175 
176 
177 
183 

190 

207 
208 


Sch.    Catherine  Marie      210 
(Capt.  Stabingtou) 


222 
223 

224 

225 

226 
227 


1884      ' 
Jane      17      noon 


17 
23 
23 
24 
25 


July 


25 


Aug.       9 
„         10 

11 

„         12 

13 
14 


4  p.m. 
6  a.m. 

6  p.m. 

5  p.m. 

6  p.m. 
2  a.m. 

7  a.m. 

4  a.m. 
4  a.m. 

7  a.m. 


4  p.m. 
noon 

5  a.m. 

8  a.m. 

4  p.m. 
4  p.m. 


11  29  S. 


14  39  S. 

15  16  S. 

16  07  S. 

17  08  S. 

4  25  S. 

13  42  S. 

14  46  S. 
23  36  S. 


E. 


126  29 


113  36 

110  08 
106  51 

114  33 

93  47 

113  42 

109  43 

59  40 


Passed  large  quantities  of 
pumice. 


14  45  S. 


Ill  20 


15  28  S  1     108  12 


16  05  S. 

16  00  S. 

16  04  S. 
16  06  S. 


104  53 

101  56 

99  05 
96  16 


Passing  vast  quantities  of 
pumice. 


Passed  throngh  large  quan- 
tities of  pumice. 


liarge  quantities  of  pumice 
floating  on  the  water. 


Passed  through  quantities 
of  pnmice  varying  in  size 
from  an  orange  to  a 
walnut  shell.  Picked 
up  some  pieces  covered 
with  barnacles  and  lim- 
pets. 

Passed  small  pieces  of 
pumice. 

Sailing  through  large  quan- 
tities of  pnmice  floating 
in  streaks  like  Gulf- 
weed. 

Still  sailing  through  quan- 
tities of  pumice. 

Still  sailing  through 
pnmice. 


»»  >>  « 

Less  pumice  to-day. 


56 


DR.  MELDRUM   ON    THE   PUMICE   AND   VOLCANIC  DUST. 


Narne^  of  Vessels. 


Day 

of 

Year. 


Montli 
and 
Day. 


Hours. 


Position  at 
Noon. 


Remarks. 


Lat. 


Long. 


Sch.      Jdsper      (Capt. 
Stannard) 


Barque  Marion  Neil 
(Capt.  Patereon) 


Barque  Jane  Maria 
(Capt.  Griffiths) 


Sch.  Coleridge  (Capt. 
Marshall) 


Barque  Caller  Ou 
(Capt.  Rae) 

S.S.  Castlehank  (Capt. 
Chevalier) 


Barque   Jane  Maria 
(Capt.  Griffiths) 


French  barque  France 
CJufrie  (Capt. 

Lavary) 


228 

230 
239 

240 
243 
245 

261 
262 

263 
271 

272 

284 

287 

288 
288 

290 

316 


1884 
Aug.     It5 

„        17 
26 

»        27 

„         30 

Sept.       1 

„        17 
18 


»        19 

»        27 

„        28 

Oct.       10 
„         13 

14 
14 

i«; 

Nov.      11 


a.m. 

a.in. 
8,  a.m. 

6  a.in. 

8  a.m. 

7.30 

a.m.  to 

noon 

noon 
4  p.m 


noon 
8  a.m. 

3  p.m. 


p.m. 

3.30 
p.m. 

5  a.m. 

5  p.m. 


23  06  S. 

20  56  S. 
14  09  S. 

14  36  S. 

15  19  S. 
9  ION. 

21  16  S. 
20  39  S. 

20  04  S. 

7  20  S. 

8  39  S. 

6  58  S. 
10  44  S. 
12  .33  S. 


15  09  S. 


20  21  S. 


E. 

O  § 

61  47 

61  01 
108  06 

106  39 
100  30 
112  11 

50  20 

51  10 

52  24 
93  02 

68  31 

102  54 
93  57 
90  19 


109  59 


58  55 


Passed  several    pieces   of 
floating  pa  mice. 


A     lot     of    pumice-stone 
floating  past. 


Passed  through  a  quantity 
of  very  small  pumice- 
stone. 

Several  pieces  of  floating 
pamice. 

Passed  large  quantities  of 
pumice  which,  apparent- 
ly, had  been  a  long  time 
in  the  water. 


Much  lava  floating  about. 


Passed  through  large  quan- 
tities of  pumice,  which 
seems  to  have  been  a 
long  time  in  the  water. 

Passed  a  large  quantity  of 
floating  pumice. 

Passed  a  large  quantity  of 
very  small  pumice. 


Large  and  small  pieces  of 
pumice  seen  frequently 
during  the  afternoon. 

Depuis  plasieurs  jours  la 
mer  est  couverte  de 
pierre-ponce. 

J'ai  parcouru  environ  une 
^tendue  de  1,200  milles 
par  latitude  sud  ou  j'ai 
rencontr^  beauoonp  de 
pierre-ponce. 


PLATE   IL 

Fig.  1. — This  drawinf^  is  reproduced  from  one  in  Yebbbek's  'Atlas/  which  was 
taken  in  October,  1883.  It  shows  the  slopes  of  the  portion  of  the  peak 
of  Rakata  which  remained  standing  after  the  great  outburst,  covered 
with  enormous  masses  of  pumice  and  dust.  In  this  covering,  streams 
have  already  cut  out  a  series  of  anastomosing  channels,  while  the  action 
of  the  sea  has  given  rise  to  the  formation  of  a  cliff. 

Fig.  2. — This  is  based  in  part  on  the  beautiful  coloured  drawing  in  Yerbeek's 
'Atlas,'  also  made  in  October,  1883,  and  in  part  on  the  photograph 
subsequently  obtained  (June,  1886),  when  some  details  before  invisible 
were  rendered  apparent  by  the  washing  of  the  surface  by  rain*  It 
must  be  remembered  that  the  surface  looked  at  is  not  a  vertical  plane 
lying  in  one  azimuth,  but  consists  of  two  planes  meeting  in  the  central 
line  at  an  angle  of  about  135^,  and  inclining  from  the  vertical  by  about 
30°.  The  lowest,  nearly  horizontal,  beds  belong  to  the  oldest  ejections  of 
the  volcano,  andesite  with  tridymite.  The  lava-currents,  tuff  beds,  and 
dykes  of  the  mass  of  the  volcano  are  composed  of  different  varieties  of 
basalt.  A  study  of  these  shows  that  lateral  eruptions  must  have  taken 
place  on  the  flanks  of  the  cone,  and  that,  as  in  the  case  of  Etna,  there 
must  have  been  a  shifting  in  the  axis  of  the  cone.  The  central  dyke 
seems  to  indicate  that  the  last  eruption  from  this  cone  must  have  con- 
sisted of  an  andesitic  material. 

For  the  skiMul  drawing  of  this  Plate,  and  of  Plate  III.,   I  am  indebted  to 
Mr.  A.  E.  TuTTON. 


Krakaioa,  Rep.  Boy.  Soc,  Com. 


PLATE  II. 


rMiS^-  ttff1f| 


Ttpo-Etobiik>  Co.,  Scolpt. 


PLATE   III. 

Sections  of  the  Lavas  of  Krakatoa. 

Fig.  1. — Section  of  the  older  andesite  of  Krakatoa,  as  seen  when  magnified  25 
diameters.  A  portion  of  the  slide  has  been  chosen  where  the  crystals  of 
felspar,  enstatite,  augite,  and  magnetite  are  more  crowded  together  than 
is  usually  the  case.  The  reddish  tint  of  the  base  when  seen  by  reflected 
light  is  due  to  the  incipient  decomposition  of  magnetite  grains  and  the 
formation  of  the  hydrated  ferric  oxides. 

Fig.  2. — Portion  of  the  base  of  the  same  rock,  as  seen  when  magnified  250  diameters. 
Microlites  of  felspar,  tridymite  (?),  and  magnetite  abound,  and  with  some 
of  pyroxene  and  hornblende  (?),  make  up  a  stony  base.  Cavities  lined 
with  tridymite,  quartz,  and  hornblende  are  seen  in  this  base. 

Fig.  3. — Zoned  and  much  corroded  crystal  of  felspar,  magnified  35  diameters,  from 
the  porphyritic  pitch  stone  of  Krakatoa.  Such  crystals,  in  xyhich  the 
glass  inclusions  are  in  great  part,  if  not  entirely,  of  secondary  origin, 
abound  in  this  i-ock.  In  some  cases,  as  shown  by  the  figure,  their  con- 
tinuity with  the  enveloping  glass  is  clearly  apparent 

Fig.  4. — Glassy  base  of  the  porphyritic  pitchstone  magnified  250  diameters.  The 
abundant  separation  of  granules  of  magnetite  all  through  the  glass 
which  envelopes  the  microlites  of  felspar  and  magnetite  is  very  well  seen 
in  this  section. 

Fig.  5. — Section  of  the  porphyritic  obsidian  of  Krakatoa,  as  seen  magnified  25 
diameters.  The  pale  brown  glass,  with  a  few  scattered  microlites,  has  in 
its  midst  a  group  of  crystals,  felspar,  enstatite,  augite,  and  magnetite, 
with  some  of  the  darker-coloured  and  less  fusible  glass  still  adhering  to 
them. 

Fig.  6. — Portion  of  the  base  of  the  same  rock  as  the  last,  as  seen  magnified  250 
diameters.  The  sparsity  of  the  microlites  of  felspar,  pjnroxene,  and 
magnetite  in  the  very  glassy  base  is  well  illustrated  by  this  section. 


Krakcuboo:  Rep.  Roy.  Soc.  Com. 


Mate  3. 


P  T  uif.  H«,dal.  I'ax-kM- ^  Oow«rdi,  lath. 


Sections  of  the  Rocks    of  Krakatoa. 


PLATE    IV. 

The  Pxtmice  Ain>  Dust  of  Ebakatoa. 

Fig.  1. — Section  of  pumioe  thrown  out  during  the  earlier  portion  of  the  Erakatoa 
eruption  (May,  1883),  cut  in  the  direction  of  the  drawn-out  fibres  of  the 
mass.  This  pumice  was  much  finer  in  grain  than  the  bulk  of  the  Krakatoa 
pumice,  and  contained  no  porphyritic  crystals.  It  is  represented  as  seen 
with  a  magnifying  power  of  50  diametera 

Fig.  2. — Cross  section  of  the  same  pumice,  magnified  50  diameters. 

Fig.  3. — Section  of  common  pumice  of  Erakatoa,  as  seen  with  a  magnifying  power 
of  50  diameters.  In. the  midst  is  seen  a  group  of  crystals  of  felspar, 
eustatite,  and  magnetite.  In  this  pumice  the  structure  is  much  coarser 
than  in  that  represented  in  Figs.  1  and  2,  and  large  irregular  air-cavities 
abound  in  it. 

Fig.  4. — Section  of  artificial  pumice,  as  seen  magnified  50  diameters,  made  by  fusing 
the  porphyritic  obsidian  of  Erakatoa.  The  escaping  gases  distend  the 
mass,  producing  a  pumice  quite  similar  in  appearance  to  the  common 
pumice  of  Erakatoa.  A  porphyritic  crystal  of  felspar  is  seen  near  the 
middle  of  the  slide. 

Fig.  5. — Pumice-dust,  which  fell  on  board  the  Arabella  when  about  1,100 
English  miles  distant  firom  the  volcano.  The  forms  of  the  particles  of 
pumice  are  well  seen.  In  this  dust,  which  fell  at  a  great  distance 
from  the  volcano,  fragments  of  the  crystallised  minerals  become  few  and 
inconspicuous.  The  particles  are  shown  as  seen  with  a  magnifying 
power  of  250  diameters. 

Fig.  6. — Similar  material,  formed  by  triturating  the  common  Erakatoa  pumice  in  a 
mortar,  as  seen  with  magnifying  power  of  250  diametera 


KrakatocL.  Rep .  Roy.  Soc.  Cotrv. 


FUUe^f. 


^"arkBrScCarmr^  dd  stlitli 


¥fc«t.Nvmn«yi&Ca  imp. 


Fumice  and  DiiBt  of  KraLkatost. 


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PART  n. 


ON  THE  AIR  WAVES  AND  SOUNDS  CAUSED  BY  THE  ERUPTION 

OF  KRAKATOA  IN  AUGUST,  1883. 

Prepared  in  the  Meteorological  Office, 

AND 

Presented  by  lAeut-General  K.  Strachey,  F.R.S.,  Chainnan  of  the  Meteorological 

CounciL 


Section  L— AIR  WAVES. 


Notes  on  this  subject  were  presented  to  the  Royal  Society  in  December,  1883,*  but 
since  that  date  observations  made  at  many  other  places,  besides  those  first  discussed^ 
have  been  obtained,  and  the  available  records  may  now  be  regarded  as  complete. 

At  the  desire  of  the  Committee  appointed  by  the  Boyal  Society  to  collect 
information  relating  to  the  eruption  of  Erakatoa,  which  occurred  in  August,  1883, 
the  present  report  has  been  drawn  up  in  the  Meteorological  OflGlce,  under  the  general 
supervision  of  the  Chairman  of  the  Meteorological  Council,  the  details  having  been 
worked  out  by  Mr.  R.  H.  Curtis,  one  of  the  senior  clerks  in  the  Meteorological 
Office,  Mr.  C.  Thompson  assisting  him  in  the  preparation  of  the  accompanying 
curves  and  diagrams. 

The  stations  from  which  barometrical  or  other  registers  supplying  evidence 
of  the  disturbance,  have  been  received,  with  the  nature  of  the  register  and  of 
the  recording  instrument,  the  general  character  of  the  data,  and  the  period  over 
which  the  observations  extend,  .in  each  case,  are  shown  in  the  annexed  Table  I. 

*  ^*  Kote  on  a  Series  of  Barometrical  DiBturbanceB  which  passed  over  Europe  between  the  27th  and 
3l8t  of  August,  1883,'*  by  Bobt.  H.  Scott,  F.K.S.,  Secretary  to  the  Meteorological  Council;  and  ''Note 
on  the  Forgoing  Paper,'*  by  Lieutenant-General  Strachey,  F.K.S.  Printed  io  the  'Proceedings  of  the 
Royal  Society,'  No.  229,  vol.  xxrvi.,  pp.  139-16]. 

I 


LTEUT.-GENERAL  STRAOHET  ON  THE  AIR  WAVES. 


TABLE    I. 

Stations  from  which  barometrical  or  other  observations  have  been  received,  with  a 
description  of  the  recording  instrunients  and  data. 


Station. 


Batayia 
Batavia 
Manila 
Melbourne 

Sydney 
Dunedin 


Wellington, 

N.Z. 


South  Georgia 

Loanda 

Mauritius 

Bombay 

Calcutta 


Data  received,  and  nature  of 
recording  instrument. 


Continuous  automatic  record 
of  gasometer  indicator. 

Hourly  observations  of  baro- 
meter and  thermometer. 

Hourly  observations  of  pres- 
sure, temperature,  wind,  ^. 

Photographic  copy  of  record 
from  a  **Kew  pattern  "photo- 
barograph,  and  also  tracing 
of  record  of  a  **  King  "  baro- 
graph. 

Tracing  of  record  obtained 
from  an  electrical  baro- 
graph (two  copies). 

Tracing  of  a  "Richard" 
barograph  record. 


Tracing    of    a    "Richard" 
barograph  record. 


Tracing  of  a  "Sprung" 
barograph  record. 

Tracing  of  a  "Richard" 
barograph  record. 

Photographic  copy  of  record 
obtained  from  a  "Kew 
pattern  "  photo-barograph. 

Photographic  copy  of  record 
obtained  from  a  "Kew 
pattern  "  photo-barograph. 

Tracing  of  record  from  a 
"  Kew  pattern "  photo- 
barog^ph;  also  zinco- 
graphed  copy  of  curve. 


General  character  of  data. 


Open  scale  and  clear  record . 


Time,  scale,  dbc.,  very  open, 
and  copies  carefully  made. 


Very  open  scale,  showing 
clearly  some  small  move- 
ments; trace  carefully  made. 

Scale  not  very  open,  and 
tracing  rather  roughly 
made. 

Scale  not  very  open,  and 
tracing  rather  roughly 
made. 

Time  scale  leather  contracted ; 
tracing  carefully  made. 

Scale  small,  but  oopy  care- 
fully made. 

Time  scale,  ^.,  sufficiently 
open,  and  copy  very  good. 


Time  scale,  &c.,  good,  and 
copy  very  good. 


Time  scale,  &c,,  good ;  trac- 
ing carefully  made. 


Duration  of  Record — 
Greenwich  Civil  Time. 


From 


To 


2  p.m., 
26th  Aug. 

1  a.m., 
21st  Aug. 

1  a.m., 
20th  Aug. 

10  a.m., 
25th  Aug. 


a.m., 
24th  Aug. 


9  a.m., 
27th  Aug. 


NOOD, 

27th  Aug. 


9  a.m., 
26th  Aug. 

10  a.m., 
27th  Aug. 

Noon, 
26th  Aug. 


10  a.m., 
26th  Aug. 


10  a.m., 
26th  Aug. 


Noon, 

28th  Aug. 

Midnight, 
81st  Aug. 

Midnight, 
10th  Sept. 

10  a.m., 
30th  Aug. 


9  a.m., 

Slst  Aug. 


a.m., 
3rd  Sept. 


10  a.m., 

3rd  Sept. 


7  a.m., 

2nd  Sept. 

10  a.m., 

3rd  Sept. 

7  a.m., 

1st  Sept. 


10  a.m., 

1st  Sept.- 


8  a.m., 

1st  S^t. 


LIEUT.-GBNERAL  BTRACHBY  ON  THE  AIE  WAVES. 
Table  I. — continued. 


59 


Station. 


Zi-Ka-Wei   ., 
(Shanghai.) 


Tokio. . 
Tiflis .  • 
PawlowBk     . . 

St.  Petersburg, 

Cracow 

Buda-Pesth  . . 
Vienna 
Berlin 
Leipeic 

Magdebnrg  • . 

Munich 

Milan.  • 
Modena 


Data  received,  and  natare  of 
recording  instrament. 


Tracing  of  record  from  a 
"  Kew  pattern  "  photo- 
barogitiph  for  1st  and  2nd 
oscillations,  and  also  of  re- 
cord from  a  "  Secchi  " 
balance  barograph  for  Ist 
to  3rd  oscillations. 

Tracing  of    record  from   a 
"King"  barograph. 

Honrlj  readings  of  the  baro- 
meter. 

Tracing  of  the  curve  from 
a  "  E^ler  "  barogragh. 


Tracing  of  the  curve  from  a 
'*  Hasler  "  barograph. 


Lithographed  copy  of  trace 
from  a  "  Kreil  "  barograph. 


Lithographed  copy  of  baro- 
gram. 

Original  barograms  from  a 
"Kreil  "barograph. 

Copy  of  barograms . . 


Copy  of  barograms . 


Lithographed  copy  of  a 
"  Sprung  "  barograph  re- 
cord. 

Lithographed  copy  of  a 
"Richard"  barograph  re- 
cord. 

Hourly  readings  of  baro- 
meter and  wind. 

Lithographed  enlarged  copies 
of  barometer  curves. 


General  character  of  data. 


Scale  of  "  Secchi  "  instru- 
ment very  open,  except  for 
time,  which  is  contracted ; 
scale  of  photo  curve  good ; 
tracings  carefully  made. 


Very  open  scale,  and  tracing 
very  carefully  made. 


Trace  not  continuous,  instru- 
ment registers  only  at  10 
min.  intervals ;  carefully 
traced. 

Trace  not  continuous,  scale 
open,  and  tracing  ap- 
parently carefully  made. 

Scale  not  very  open ;  trace 
shows  scarcely  any  signs  of 
distarbance. 

Scales  open,  and  oscillations 
clearly  shown. 

Record  at  5  min.  intervals ; 
scales  fairly  open. 

Record  at  15  min.  intervals ; 
time  scale  rather  contracted. 

Very  open  scales 


Good,  but  time  scale  rather 
contracted. 


Good  record,  but  time  scale 
very  contracted. 


Curves  have  been  very  much 
enlarged  from  the  originals, 
and  have  very  open  scales. 


Duration  of  Record — 
Greenwich  Civil  Time. 


From 


To 


2  a.m., 
22nd  Aug. 


9  a.m., 
27th  Aug. 

1  a.m., 
26th  Aug. 

Midnight, 
26th  Aug. 


6  p.m., 
26th  Aug. 


Noon, 
27th  Aug. 


Midnight, 
26th  Aug. 

Noon, 
27th  Aug. 

Noon, 
26th  Aug. 

11  a.m., 
27th  Aug. 

Midnight, 
26th  Aug. 


Midnight, 
26th  Aug. 


Noon, 
25th  Aug. 

Noon, 
26th  Aug. 


6  p.m., 

29th  Aug. 


9  a.m., 

2nd  Sept. 

Midnight, 
2nd  Sept. 

Midnight, 
30th  Aug. 


Midnight, 
30th  Aug. 


Noon, 

1st  Sept. 

Midnight, 
30th  Aug. 

Noon, 

29th  Aug. 

Noon, 

5th  Sept. 

5  p.m., 

3l8t  Aug. 

Midnight, 
1st  Sept. 


3  a.m., 

31st  Aug. 


11  a.m., 

1st  Sept. 

Noon, 

3rd  Sept 


60 


LIEDT.-GENERAL  STRACHBT  ON  THE  AIR  WAVES. 
Table  I. — continued. 


Station. 


Rome.  •  • 
Palermo 
San  Fernando . 

Lisbon 


Serra    da  Es- 
trella. 

Coimbra 

Paris — 
ParoSt.Manr 


Montsonris. . 

Brussels 
Greenwich    •  • 

Eew  •  •  • • 

Oeldeston 
Oxford 
Falmontb 
Valencia 
Armagh        •• 


Data  receiredy  and  natnre  of 
recording  instrument. 


Tracing    of    a    "Richard" 
barograph  record. 

Tracing  of  a  "  Secohi "  baro- 
graph curve* 


Photographic  copy  of  record 
irograph 
Salleron,  of  Paris, 


from  barograph  made  by 


Tracing  of  a  "Redier"  baro- 
gram. 

Tracing  of  a  "Richard" 
barograph  record. 

Original  curve  of  a  "Kew 
pattern  "  photo-barog^ph. 

Tracing  of  curve  of  a  "  Re- 
dier "  barograph,  with 
hourly  readings  of  baro- 
meter. 

Trace  of  record  obtained 
from  a  balance  barometer. 


General  character  of  data. 


Lithographed  copy  of  record 
from  a  photo-barograph. 

Tracing  and  photographic 
copy  of  record  of  photo- 
barograph. 

Original  curve  from  a  "  Kew 
pattern  "  photo-barograph. 

Tracing  of  record  from  a 
"Re£er"  barograph. 

Original  curve  of  a  "  Kew 
pattern  "  photo-barograph. 

Original  curve  of  a  "  Kew 
pattern  "  photo-barograph. 

Original  curve  of  a  "Kew 
pattern  **  photo«barograph. 

Original  curve  of  a  "Kew 
pattern  **  photo-barograph. 


Very  clear,  but  scales  small 


Trace  carefully  made,  but 
time  scale  very  contracted. 

Open  scale  and  very  good 
curve,  but  the  time  is 
doubtful. 

Very  contracted  time  scale, 
but  clearly  traced. 

Small  time  scale 


Very  good  curves,  and  open 
scales. 

Time  scale  rather  contracted, 
but  movements  clearly 
shown  and  trace  carefully 
made. 

i  Oscillations  very  well  shown, 
I  but  time  scale  rather  con- 
]     tracted. 

Good  clear  trace 


Open  scales,  and  very  good 
copies. 

Open  scales,  and  good  curves 


Open  scales,  and  traces  care- 
fuUy  made. 

Open  scales,  and  good  curves 


Open  scales,  and  good  curves 


Open  scales,  and  good  curves 


Open  scales,  and  good  curves 


Duration  of  Record — 
Greenwich  Civil  Time. 


From 


Noon, 
20th  Aug. 

7  a.m., 
24th  Aug. 

10  ajn.» 

26th  Aug. 


Midnight, 
25th  Aug. 

8  a.m., 
27th  Aug. 

Midnight, 
26th  Aug. 

Midnight, 
25th  Aug. 


Midnight, 
25th  Aug. 


8  a.m., 
26th  Aug. 

Noon, 
26th  Aug. 


Midnight, 
26th  Aug. 

Midnight, 
25th  Aug. 

10  a.m., 
25th  Aug. 

Midnight, 
26th  Aug. 

Midnight, 
26th  Aug. 

Midnight, 
26th  Aug. 


To 


Noon, 

2nd  Sept. 

7  a.m., 

5th  Sept. 

10  a.m., 
dOth  Aug. 


Midnight, 
80th  Aug. 

6  a.in., 

31st  Aug. 

Midnight, 
30th  Aug. 

Midnight, 
30th  Aug. 


Noon, 

29th  Aug. 


8  a.m., 

1st  Sept. 

Noon, 

2nd  Sept. 


Midnight, 
1st  Sept. 

Midnight, 
2nd  Sept. 

10  a.m., 
31st  Aug. 

Midnight, 
1st  Sept. 

Midnight, 
1st  Sept. 

Midnight, 
1st  Sept. 


LIEXJT.-GBNBRAL  STRACHEY  ON  THE  AIR  WAVES. 
Table  I. — continued. 


61 


Station. 


Liverpool 

Stonjlmrst 

Olasgow 

Aberdeen 

Toronto 

New  York 


Hastings -on 
Hudson,  N.Y. 


Washington . . 


Mexico 


Havana 


Cordoba 


Data  received,  and  nature  of 
recording  instrument. 


Tracings  of  record  of  a 
"Bang**  barograph. 

Original  curve  of  a  "  Kew 
pattern  *'  photo-barograph. 

Original  curve  of  a  "Kew 
pattern  *'  photo-barograph. 

Original  curve  of  a  "Kew 
pattern  "  photo-barograph. 

Photographic  copy  of  record 
of  a  "  Kew  pattern  ** 
photo-barograph. 

Copies  of  record  obtained 
from  a  "Draper"  pencil 
barograph. 

Copy  of  record  obtained 
from  a  "  Draper  **  baro- 
graph. 

Copies  of  trace  from  a 
"  Gibbon  **  electric  baro- 
graph. 


.Copy  of  trace  from  baro- 
graph, apparently  an  ane- 
roid recording  only  hourly. 


Original  records  of  baro- 
graph, anemograph,  ther- 
mograph, &o. 


Curve  of  hourly  readings 
obtained  from  an  hourly- 
recording  aneroid. 


General  character  of  data. 


Very  open  scales,  and  care- 
fully traced  copies. 

Open  scales,  and  good  curves 


Open  scales,  and  good  curves 


Open  scales,  and  good  curves 


Open  scales,  and  good  copies 
of  traces. 


Open  scale,  and  clear  trace.  • 


Very  contracted  time  scale ; 
clear  trace. 


Very  open  scales,  and  careful 
copies. 


Very  small  time  scale ;  trace 
not  continuous,  given  at 
the  hours  only. 

Time  scale  very  contracted, 
and  barometer  trace  some- 
what thick,  but  the  earlier 
oscillations  are  well  shown. 

Trace  interpolated  between 
the  hours. 


Duration  of  Record — 
Greenwich  Civil  Time. 


From 


9  a.m., 
27th  Aug. 

Midnight, 
26th  Aug. 

Midnight, 
26th  Aug. 

Midnight, 
26th  Aug. 

Noon, 
26th  Aug. 


Midnight, 
25th  Aug. 


3  p.m., 
26th  Aug. 


Noon, 
26th  Aug. 


1  a.m., 
26th  Aug. 


Noon, 
23rd  Aug. 


Midnight, 
25th  Aug. 


To 


9  a.m., 

4th  Sept. 

Midnight, 
1st  Sept. 

Midnight, 
1st  Sept. 

Midnight, 
1st  Sept. 

Noon, 

3rd  Sept. 


Midnight, 
Ist  Sept. 


3  p.m., 

2nd  Sept. 


Noon, 

2nd  Sept. 


11  p.m., 
2nd  Sept. 


Noon, 

6th  Sept. 


Midnight, 
2nd  Sept. 


The  geographical  position  of  the  stations  from  which  the  continuous  barometric 
registers  have  been  received,  and  which  supply  the  data  now  exclusively  dealt  witlj, 
their  latitudes,  longitudes,  and  distances  from  Erakatoa,  in  degrees  of  a  great  circle, 
are  shown  in  the  following  Table  U. 


62 


LIEUT.-aENERAL  STBACHEY  ON  THE  AIR  WAVES. 


TABLE  II. 

Geographical  position  of  Erakatoa,  and  of  the  principal  Stations  from  which  data 
have  been  supplied. 


Distance  in  Degrees  of  a  Great 

Circle  from  Krakatoa. 

Station. 

Latitude. 

Longitude. 

THr<v>f. 

Through 

X.'Al^W. 

Antipodes. 

Erakatoa           

6      9  8. 

105    22  8. 

O               / 

•  • 

o             / 

•  a 

Batavia  . . 

6      9  s. 

106    48  E. 

1    22 

358    88 

Melbourne 

37    60s. 

144    68  E. 

47    53 

312      7 

Sydney  .. 

33    54  8. 

161     14  E. 

50    33 

309    27 

Danedin.. 

45    52  8. 

170    37 «. 

68    27 

291    83 

Wellington,  N.Z 

41    16  8. 

174    47  b. 

70    31 

289    29 

South  Georgia  . 

54    31s. 

36      6w. 

111    22 

248    38 

Loanda  .. 

8    49  s. 

13      7e. 

91    17 

268    43 

ManritioB 

20      6  8. 

67    33  E. 

48    29 

311    31 

Bombay . . 

18    64  N. 

72    49  E. 

40    42 

319    18 

Calcutta  . . 

22    33  N. 

88    21  E. 

33      8 

326    62 

Zi-Ka-Wei 

81    12  N. 

121    26  E. 

40    22 

319    38 

Tokio      . . 

.        35    41  N. 

139    46  E. 

62    41 

307    19 

Pawlowsk 

59    41  N. 

30    29  E. 

87    49 

272    11 

St.  Peterabnrg  . 

59    66  k. 

80    18  E. 

87    57 

272      3 

Bnda-Pesth       . 

47    30  H. 

19      2e. 

92      5 

267    55 

Vienna   .. 

48    12  N. 

16    22  E. 

93    68 

266      2 

Berlin     . . 

52    30  N. 

13    19  E. 

96      7 

263    53 

Leipsic   .. 

51    20  N. 

12    24  E. 

96    36 

263    24 

Magdeburg 

. 

52      9n. 

11     88  E. 

97    10 

262    60 

Munich  .. 

48      9  k. 

11    34  s. 

97      6 

262    54 

Modena  . . 

44    38  N. 

10    55  E. 

97    30 

262    30 

Rome 

.       41    54  N. 

12    29  X. 

96    15 

268    45 

Palermo . . 

88      7h. 

13    21  E. 

96    20 

264    40 

San  Fernando    . 

36    28  N. 

6    13  w. 

111      1 

248    59 

Lisbon    . . 

38    42  N. 

9      8w. 

112    52 

247      8 

Coirobra.. 

40    13  N. 

8    26  w. 

112      3 

247    57 

Serra  da  Estrella 

40    25  H. 

7    35w. 

111    25 

248    86 

Paris — 

Pare  St.  Manr 

48    48n. 

2    31  E. 

103    10 

256    50 

Montsonris. 

48    49  N. 

2    20  E. 

103    10 

266    50 

Brussels . . 

50    52  k. 

4    21  E. 

101    48 

258    17 

Greenwich 

51    29  N. 

0      0 

104    20 

255    40 

Kew 

51    28  k. 

0    19  w. 

104    32 

265    28 

Geldeston 

52    28  k. 

1    32  E. 

103    16 

256    44 

Oxford   .. 

51    46  N. 

1    16  w. 

105      2 

254    58 

Falmouth 

50      9  k. 

5      4w. 

107    45 

252    15 

Valencia.. 

51    55  H. 

10    18  w. 

110    29 

249    31 

Armagh  . . 

54    21  N. 

6    89  w. 

107    44 

252    16 

LiTerpool 

53    24  k. 

3      4w. 

105    52 

254      8 

Stonyhurst 

53    51  K. 

2    28w. 

105    24 

254    36 

Glasgow.. 

55    63  k. 

4    18  w. 

106      2 

253    58 

Aberdeen 

67    10  k. 

2      6w. 

104    32 

255    28 

Toronto  . . 

43    39  k. 

79    23  w. 

142    12 

217    48 

New  York 

40    43n. 

74      Ow. 

146    24 

214    86 

Washington 

38    64  k. 

77      2w. 

147    12 

212    48 

Havana  ..         . 

23    10  k. 

82    22  w. 

161    20 

198    40 

Mexico    . . 

19    25  k. 

99      6w. 

153    24 

206    36 

LIBUT.-GENERAL  STRACHBY  ON  THE  AIR  WAVES.  63 

The  general  features  of  the  remarkable  atmospheric  disturbance  caused  by  the 
great  explosion  on  the  morning  of  August  27th,  which  appears  to  have  been  the  effect 
of  the  final  paroxysm  of  the  volcano,  and  of  which  alone  well-defined  indications 
susceptible  of  identification  and  measurement  have  been  preserved  by  the  barometric 
registers,  will  be  seen  from  Plate  VII.,  which  reproduces,  on  an  enlarged  scale,  the  forms 
of  the  trace  obtained  at  selected  stations  where  the  record  is  most  nearly  perfect,  on 
the  several  successive  repetitions  of  the  great  aerial  oscillation,  of  which,  in  many 
cases,  seven  were  distinctly  observed.  For  some  time  before  the  great  catastrophe, 
minor  explosions  occurred,  of  which  indications  may  be  found  in  many  of  the 
photographic  registers,  especially  those  from  the  stations  least  removed  from  Krakatoa, 
the  trace  being,  so  to  speak,  roughened  by  many  small  irregularities,  giving  it  an 
appearance  very  different  from  that  of  the  smooth  line  which  is  its  usual  character. 

In  the  communication  on  this  subject  before  made  to  the  Royal  Society,  it  was 
shown  that  the  observed  facts  clearly  established  that  the  successive  repetitions  of 
the  disturbance  at  the  numerous  stations,  after  varying  intervals  of  time,  were  caused 
by  the  passage  over  them  of  an  atmospheric  wave  or  oscillation,  propagated  over  the 
8ur£eice  of  the  globe  from  Krakatoa  as  a  centre,  and  thence  expanding  in  a  circular 
form,  tni  it  became  a  great  circle  at  a  distance  of  180°  from  its  origin ;  after 
which  it  advanced,  gradually  contracting  again, .  to  a  node  at  the  antipodes  of 
Krakatoa;  whence  it  was  reflected  or  reproduced,  travelling  backwards  again  to 
Ejukatoa,  from  which  it  once  more  returned  in  its  original  direction ;  and  in  this 
manner  its  repetition  was  observed  not  fewer  than  seven  times  at  many  of  the 
stations,  four  passages  having  been  those  of  the  wave  travelling  from  Krakatoa,  and 
three  those  of  the  wave  travelling  from  its  antipodes,  subsequently  to  which  its 
traces  were  lost. 

The  barometric  disturbance  caused  by  the  great  explosion  began  with  a  more  or 
less  sudden  rise,  on  the  summit  of  which  two  or  three  minor  oscillations  are  visible, 
followed  by  a  deep  depression,  which  was  succeeded  by  a  less  well  marked  rise,  and  by 
other  depressions  and  rises,  the  whole  disturbance  extending  over  a  period  of  nearly 
two  hours.  Such  are  the  characters  of  the  traces  of  almost  all  the  self-recording  instru- 
ments on  the  occurrence  of  the  first  two  waves,  and  they  are  very  clearly  seen  in  the 
photographic  barograms  obtained  at  Bombay,  Melbourne,  Mauritius,  and  the  British 
Observatories.  The  traces  of  these  two  passages  of  the  wave  are,  in  many  instances, 
remarkably  alike,  although  the  second  oscillation  must  have  crossed  the  first  at  or 
near  the  Antipodes  of  Krakatoa.  The  wave,  however,  gradually  became  deformed 
during  its  progress  from  and  to  the  point  where  it  originated,  and  eventually  lost  the 
characters  above  described.  On  the  third  and  fourth  recurrence  the  disturbance  is 
commonly  indicated  by  a  sudden  rise,  which  has  the  appearance  of  replacing  the 
deep  central  depression  of  the  first  and  second  passages. 

From  the  irregularity  of  the  form  of  the  wave,  and  its  want  of  persistency, 
together  with  the  considerable  time  over  which  it  extended,  there  has  been  some 

k2 


64  LIEUT.-GBNBRAL  STRACHET  ON  THE  AIR  WAVES. 

unavoidable  uncertainty  in  fixing  the  exact  moment  of  the  passage  of  the  same  phase 
of  the  disturbance  in  the  several  waves  over  the  various  stations  ;  but  the  deep 
depression  which  immediately  followed  the  initial  rise  appears,  on  the  whole,  to  be  the 
most  persistent  and  easily  recognised  feature  in  the  first  two  passages  of  the  wave ; 
and  where  it  can  be  identified  it  has  been  taken  as  the  standard  to  which  reference 
has  been  made,  especially  in  fixing  the  time  of  the  occurrence  of  the  great  explosion. 

There  can,  however,  be  no  doubt  that  the  rise  of  the  barometer,  indicating  a 
sudden  increase  of  pressure,  was  the  first  and  direct  result  of  the  explosion,  and  that 
the  succeeding  fall  of  the  barometer,  or  decrease  of  pressure,  together  with  all  the 
subsequent  oscillations,  were  mechanical  consequences  of  the  original  shock,  which 
in  the  nature  of  the  case  required  some  considerable  time  for  their  development. 
These  remarks  have  an  obvious  bearing  on  the  manner  in  which  the  exact  time  of  the 
final  explosion  may  be  inferred  from  the  observed  times  of  the  atmospheric  disturb- 
ances, a  point  to  which  attention  will  subsequently  be  given. 

It  may  here  be  remarked  that  the  theoretical  investigations  of  Lord  Rayleigh 
indicate  that  the  sudden  expansion  of  an  elastic  gas,  supposed  to  be  confined  in  a 
spherical  envelope,  would  cause  an  oscillation  which  begins  with  a  wave  of  compression, 
followed  by  one  of  expansion  ;  a  form  which  appears  to  correspond  with  that  of  the 
disturbance  now  under  consideration.  According  to  the  same  authority  the  amplitude 
of  the  wave  diminishes  as  the  square  root  of  the  distance  travelled  by  it.  The  data 
do  not  admit  of  any  positive  opinion  being  formed  as  to  whether  this  held  good  in  the 
present  case,  but  there  is  at  least  nothing  to  suggest  any  departure  from  such  a  law. 

Plate  VIII.  gives  a  representation,  on  a  reduced  and  uniform  scale  of  time  and 
vertical  extent,  of  the  observed  disturbances  as  shown  on  the  various  barograms,  at 
the  different  stations  at  which  the  registers  are  sufficiently  well  defined  for  reproduc- 
tion in  this  manner.  The  positions  on  the  traces  which  have  been  taken  to  indicate 
the  standard  point  of  the  oscillation,  selected  as  before  explained,  are  marked  for 
facility  of  reference  ;  but  it  must  be  explained  that  the  reduction  of  the  trace  in  most 
cases  renders  the  identifications  far  less  obvious  than  they  actually  are  on  the  original 
registers. 

The  times  at  which  the  successive  passages  of  the  wave  were  observed  at  the 
several  stations  (reckoned  in  all  cases  in  hours  and  minutes  from  0  hours  of  the  27th 
of  August,  1883,  Greenwich  Mean  Time,  civil  reckoning)  are  shown  in  the  annexed 
tables. 

Table  III.  gives  the  times  of  passage  of  the  waves  travelling  from  Krakatoa 
towards  its  antipodes.  These  passages  of  the  waves  are,  for  convenience,  numbered 
as  I.,  Ill,  v.,  and  VII. 


LIEUT.-GENEBAL  STRAOHBT  ON  THE  AIE  WAVES, 


65 


TABLE  III. 

Observed  times  of  the  successive  passages  of  the  waves  travelling  from  Krakatoa 
towards  its  Antipodes;  reckoned  fix)m  0  hours  of  August  27th,  1883,  Greenwich 
Mean  Time,  civil  reckoning. 


Passage  of  Wave. 

-    -- 

Station. 

I. 

m. 

V. 

vn. 

hrs. 

min. 

hrs.    min. 

hrs. 

min. 

hrs.    min. 

Melboame 

8 

14 

43      12 

•  • 

•  • 

Sydney  . . 
Dnnedin. . 

8 
10 

24 
15 

43      18 
45      15 

78 

39 

? 

•  • 

p 

WeUiniflon,  N.Z 

10 

20 

45      45 

•     ? 

J) 

Soath  Georgia  . . 

15 

24 

48      24 

? 

? 

Loanda  . . 

12 

18 

47      15 

82 

23 

117      23 
mean. 

ManritiTis 

8 

17 

42      60 

77 

26 

112      10 

Bombay 

7 

26 

44        0 

? 

? 

Calcutta 

6 

47 

43      22? 

? 

? 

Zi-Ka-Wei         

7 

27 

42      54  P 

•  « 

•  • 

Toldo 

8 

51 

44      12? 

P 

? 

Pawlowsk          

12 

18 

49      18 

86 

38 

•  • 

St.  Petersburg  . . 

12 

14 

48      39 

85 

44? 

•  « 

Bada-Pesth 

12 

30 

48      55 

84 

45? 

•  • 

Vienna  . . 

12 

34 

49        9? 

•  • 

•  • 

mean. 

Berlin 

12 

52 

49      37 

86 

14 

122      .37? 

Leipsic  .. 

14 

0? 

? 

9 

•  • 

Magdebntg        

12 

59 

49      28 

84 

31 

? 

Manich 

12 

35 

49      30 

85 

0 

,  , 

Modena 

12 

51* 

49      11* 

85 

26» 

121      86» 

Bome     . .         . .         . .         . . 

13 

0 

48      55 

P 

P 

Palermo 

13 

37  ?t 

? 

P 

? 

San  Fernando   . . 

13 

22 

49      12 

•  • 

•  • 

Lisbon    .. 

14 

17 

50      12 

P 

•  •     . 

Serra  da  Estrella          

13 

50? 

50        0? 

P 

•  • 

Coimbra. . 

14 

20 

50      10 

P 

,  , 

Paria— 

Pare  St.  Manr 

13 

41 

50        1 

86 

61 

•  • 

MontsoQiis 

13 

34 

49      54 

,  , 

•  • 

Brossels 

13 

28 

50        5 

86 

36 

? 

Greenwich         

13 

45 

60      13 

87 

2 

124        6P 

Kew 

13 

48 

50      12 

87 

10 

124      10 

Geldeston          

13 

39 

50        2 

86 

59 

123      31 

Oxford 

13 

53 

50      15 

? 

•  ■ 

Falmouth 

14 

4 

50      25 

P 

P 

Valencia 

14 

25 

60      51 

87 

42 

9 

Armagh  . . 

14 

15 

50      45 

87 

22 

124      30? 

Liverpool           ..         

Stonyhnrst        

13 

58 

50      25 

87 

20 

124        5P 

13 

55 

50      27 

87 

0 

124      10 

•  Times  given  by  Professor  Bagona,  Director  of  Bojal  Observatory,  Modena. 
t  This  time  differs  slightly  from  that  given  by  Professor  Cacciatore  of  Palermo  Observatory. 
time  scale  of  the  enrve  is  very  contracted. 


The 


66 


LIEUT-GENERAL  STBACHET  ON  THE  AIR  WAVES* 


Table  III. — continued-. 


station. 


Passage  of  Wave, 


III. 


VIL 


Glasgow 

Aberdeen 

Toronto  . . 

New  York 

Hastings-on-Hudson,  N.Y 

Washington 

Mexico    • . 

Havana  . . 

Cordoba 


hi*8.    min. 
14        2 


hrs.    min. 
50      38 


13 
1? 
17 
17 

18 

19 


52 
83 
53 
56? 
0 

? 

0?» 

? 


50 
55 
55 
55 
55 

55 


32 
18 

21 

41? 

33 

? 

50? 

? 


hrs.    min. 
87      15 


87 
^92 


12 
0 


92       11 


hrs.    min. 
124      20 


124 
127 


128 


20 
43 

P 

? 
0? 

? 

? 

? 


*  This  oscillation  occurred  a  little  after  19  honrs,  but  the  time  scale  is  too  contracted  to  allow  of 
the  time  being  obtained  with  much  exactness. 

Note. — ^A  ?  inserted  alone  in  the  column  indicates  that  the ''Wave"  cannot  be  identified  in  the 
trace.  When  a  blank  is  inserted  in  the  column  it  indicates  that  no  trace  has  been  received  for  that 
period. 

Table  IV.  gives  the  times  of   the  passage  of  the  waves  returning    towards 
Erakatoa  from  its  Antipodes.     These  are  numbered  as  II.,  IV.,  and  VI. 


TABLE  IV. 

Observed  times  of  the  successive  passages  of  the  waves  returning  towards 
Erakatoa^  after  having  passed  its  Antipodes;  reckoned  from  0  hours  of  August 
27th,  1883,  Greenwich  Mean  Time,  civil  reckoning. 


Station. 


Melbourne         • 
Sydney   . . 
Dnnedin 
WeUington,  N.Z 
South  G^rgia  • 
Loanda  •. 
Manritins 
Bombay . . 
Calcutta.. 
Zi-Ka-Wei 


Passage  of  Wave. 


VI. 


hrs.    mill. 

•  • 

? 

? 

? 

? 

102  '    23 

105      55 

P 

? 

•  • 

LIEUT.-GENBBAL  STEACHEY  ON  THE  AIR  WAVES. 
Table  IV. — continued. 


67 


Station. 

Passage 

of  Ware. 

XL 

IV. 

VI. 

hrs.    min. 

hrs.    min. 

hrs.    min. 

Tokio 

34      20 

? 

P 

Pawlowsk          

29      28 

63      53 

•  • 

St.  Petersburg 

29      24 

63      49 

•  • 

Bada-Peath 

28      20 

64      10 

•  • 

Vienna 

29        9 

•  • 

,  , 

Berlin 

28      37 

63      14 

P 

Leipsic 

28      40? 

? 

P 

Magdebnrg        

28      36 

63      18? 

98        8? 

Mnnich  . . 

28      30 

63      40 

P 

Modena 

28      16* 

62      36» 

97      31» 

Borne 

28      55 

? 

? 

Palermo.. 

29      27?t 

? 

? 

San  Fernando    . . 

27        0 

62        2 

•  • 

Lisbon 

27      17 

62      32 

•  • 

Serra  da  Estrella         

27      30? 

62        0? 

P 

Coimbra            ..         

27      15 

62      23 

•  ♦ 

Paris: — 

Pare  St.  Manr 

28      21 

63        4 

•  • 

Montsonris            

28      21 

•  • 

«  • 

Bmssels . . 

28      23 

62      40? 

97      53 

Greenwich 

27      68 

62      45 

98       0 

Zew        

28        5 

62      42 

98        0 

Geldeston          

28        6 

62      44 

98        4 

Oxford 

28        5 

62      35 

? 

Falmonth          

27      43 

62      27 

98        0 

Valencia. . 

27      15 

62      10 

97      13 

Armagh . .          . .         . .          . .         , . 

27      32 

62      22 

97        7 

Liverpool 

Stonyhnrst        

27      41 

62      40 

97      10? 

27      45 

62      35 

97      10 

Glasgow 

27      45 

62      26 

97        8 

Aberdeen 

27      52 

62      32 

98      20 

Toronto 

25      48 

57      53 

91      18 

NewTork         

25      26 

58      18 

P 

Hastings-on-Hadson,  N.T.     . . 

25      26? 

58      16? 

P 
f9l        81 

Washington 

25      20 

57      61 

\        or     \? 
1.90      23j 

Mexico   .. 

P 

P 

P 

Havana  ..         

24      15? 

67        0? 

? 

Cordoba 

P 

P 

? 

*  Times  given  by  Prof.  Bagona,  Director  of  "BiOjal  Observatory,  Modena. 

t  This  time  differs  slightly  &om  that  given  l^  Prof.  Cacdatore,  of  Palermo.  The  time  scale  of 
the  cnrve  is  very  contracted. 

NOTK. — ^A  ?  inserted  alone  in  the  colamn  indicates  that  the  "Wave"  cannot  be  idoitified  in  the 
trace.  When  a  blank  is  inserted  in  the  column,  it  indicates  that  no  trace  has  been  received  for  that 
period. 

From  the  times  thus  recorded  may  be  deduced  the  probable  precise  moment  of 
the  oocurrence  of  the  great  explosion,  of  which  there  is  otherwise  no  satis&ctory  or 
complete  evidence,  as  well  as  the  velocities  of  the  wave's  transmission  in  its  course 
round  the  earth. 


68 


LIEUT-GENERAL   STRACHEY  ON  THE  AIE  WAVES. 


But,  as  will  be  more  fully  shown  hereafter,  the  velocity  of  transmission  was  not 
uniform  in  all  directions,  nor  did  it  remain  constant  as  the  wave  advanced.  In 
order,  therefore,  to  determine  the  most  probable  moment  of  the  origin  of  the  wave, 
it  has  been  considered  best  to  deal  only  with  the  data  obtained  from  the  stations 
nearest  to,  and  immediately  surrounding,  Krakatoa: — ^viz.,  Calcutta,  Zi-Ka-Wei 
(Shanghai),  Bombay,  Melbourne,  Mauritius,  and  Sydney ;  at  all  which  the  records  of 
the  first  passage  of  the  wave  are  well  defined  and  satisfactorily  comparable,  while 
their  distances  from  Krakatoa  are  not  so  great  as  to  make  it  likely  that  important 
variations  of  the  velocity  of  the  wave  took  place  during  the  time  occupied  in 
reaching  them. 

If  T  is  the  time  of  the  origin  of  the  wave,  which  is  to  be  determined  ;  t,  the 

time  of  the  passage  of  the  wave  at  any  station ;  c?,  the  distance  in  degrees  from  the 

point  of  origin ;  and  V,  the  velocity  of  the  wave's  transmission,  assumed  to  be  the 

same  in  all  cases  ;  then 

d 


V  = 


«-T 


and  representing  by  d^^  c^^,  • .  •  •  d^^  the  several  distances  of  the  six  stations  fi*om 
Krakatoa  ;  by  t^,  tg, . . .  •  <6>  tbe  several  observed  times  of  passage  of  the  wave ;  and 
by  ^{d)  and  ^{t)  the  sums  of  the  distances  and  times,  we  shall  have  for  the  most 
probable  values  of  T  and  V. 

T  =  ^')'  ^^^J^^f^''^  =  3.54  hours  =  3hrs.  32min.  G.M.T. 

V  =  ^t^^f^zWf,J^  =   10'31  degrees,  or  713  English  miles  per  hour. 
6  2\at)  —  S  \t).  A \d) 

The  residual  errors  of  observation,  assuming  the  above  values,  are  shown  in  the 

following  Table  V. 


TABLE 

V. 

Station. 

d. 

t. 

t-T. 

d-i-V. 

Error  in 
Time. 

d 

Error  in 
Velocity. 

0 

Hn. 

Hn. 

Hrs. 

Hr. 

0 

0 

Calcutta           

3313 

6-78 

3-24 

3-21 

-03 

10-23 

-08 

Zi-Ka-Wei 

40-37 

7-45 

3-91 

8-92 

+  •01 

10?2 

+  01 

Bombay 

40-70 

7-43 

3-89 

3-95 

+  06 

10-46 

+  15 

Melbourne 

47-88 

8-23 

4-C9 

4-64 

-06 

10-21 

-10 

Mauritius 

48-48 

8-28 

4-74 

4-70 

-•04 

10-23 

-•08 

Sydney 

50-65 

8-40 

4-86 

4-90 

+  04 

10-40 

+  09 

From  which  it  may  be  concluded  that  the  probable  error  of  the  deduced  time  of 
origin  of  the  wave  is  ±  '04  hour,  or  about  2^  mins. ;  and  that  of  the  velocity  of 
the  wave  ±  '09  degree,  or  6  miles  per  hour. 


LIEUT..GBNERAL  STRACHEY  ON  THE  AIR  WAVES.  C9 

As  was  before  observed,  however,  the  phase  of  the  oscillation  taken  as  the 
standard,  in  reckoning  the  times  of  the  wave's  passage  over  the  several  stations,  is 
not  the  initial  extraordinary  rise,  but  the  lowest  part  of  the  depression  following  it. 
It  is  not  easy  to  define  precisely  the  true  commencement  of  the  disturbance  which 
precedes  the  passage  of  the  standard  phase  of  the  oscillation  over  the  several  stations, 
and  there  may  be  an  error  of  at  least  5  minutes  in  the  determination  that  has  been 
adopted  as  most  probable.  This,  however,  gives  for  the  mean  of  five  of  the  last- 
mentioned  stations  36  minutes  earlier,  and  all  agree  within  4  minutes  of  that  value. 
Sydney  is  excluded  from  this  determmation,  as  the  trace  is  too  irregular  to  admit 
of  a  satisfactory  result  being  obtained. 

Consequently  the  probable  moment  of  the  great  explosion  was  3  hrs.  32  mins., 
mtntuf  36  mins.  =  2  hrs.  56  mins.  G.  M.  T.,  or  9  hrs.  58  mins.  local  time. 

A  corroboration  of  the  conclusion  thus  arrived  at,  is  afibrded  by  the  register  of 
the  gasometer  indicator  at  Batavia,  which  fortunately  is  available,  and  which  in  the 
absence  of  a  continuous  barometric  record,  supplies  a  fairly  trustworthy  indication  of 
the  atmospheric  pressure  at  the  time  in  question.  Plate  IX.  is  a  slightly  reduced 
facsimile  of  a  portion  of  this  register  for  the  first  half  of  August  27th.* 

The  distance  of  Krakatoa  from  Batavia  being  1^  22',  the  wave,  with  the  velocity 
before  calculated,  would  reach  the  latter  place  in  8  mins.,  so  that  it  would  have  been  felt 
there  at  3  hrs.  4  mins.,  G.  M.  T.,  or  10  hrs.  11  mins.,  local  time.  The  gasometer  shows 
a  sudden  and  most  extraordinary  increase  of  pressure  at  some  time  between  10  hrs.  15 
mins.  and  10  hrs.  20  mins.  a.m.,  local  time,  agreeing  as  exactly  with  that  above  arrived 
at  ajs  could  be  expected  from  the  somewhat  rough  character  of  the  trace,  the  inertia 
of  the  recorder,  and  the  possible  error  of  the  clock  at  a  non-scientific  establishment. 

The  oscillations  of  the  gasometer  indicator  were  very  numerous  and  violent  on 
the  day  of  the  great  explosion,  but  following  the  maximum  increase  just  referred  to, 
there  appears  to  have  been  a  maximum  reduction  of  pressure  between  10  hrs.  40  mins. 
and  10  hrs.  50  mins.  local  time,  corresponding  therefore  with  the  maximum  fall  shown 
in  the  barometric  traces  of  the  wave.  It  has  not  been  possible  to  connect  any  other 
of  the  gasometer  indicator  oscillations  with  any  available  recorded  barometric  disturb- 
ances, and  from  this  it  must  be  inferred  that  the  explosion  at  2  hrs.  56  mins.,  G.  M.  T,, 
was  far  more  violent  in  its  character  than  any  of  the  others. 

The  intervals  of  time  between  the  origin  of  the  great  wave  and  its^r^^  passage 
over  the  several  stations,  direct  from  Krakatoa ;  as  well  as  the  time  intervals  between 
the  successive  subsequent  recurrences  bf  the  wave  in  its  progress  round  the  earthy 

*  On  the  original  the  trace  at  about  10  hrs.  15  mins.  passes  beyond  the  limits  of  the  diagram,  and 
it  is  quite  possible  that  the  atmospheric  pressure  on  the  gasometer  at  that  moment  may  have  been 
snfficient  to  have  caused  the  pencil  to  rise  even  higher  than  it  did,  had  the  construction  of  the  recording 
apparatus  allowed  of  its  doing  so.  The  ^gures  on  the  right  of  the  diagram  gi^e  the  indicated  pressure 
on  the  gasometer  in  millimetres  of  water,  while  those  on  the  left  give  the  equivalent  pressures  in 
inches  of  mercury.  It  must  b^  remembered,  however,  that,  in  order  to  get  the  absolute  pressure  on 
the  gasometer,  the  figures  must  in  each  case  be  doubled. 

L 


70 


LIEUT-GENERAL  STRACHEY  ON  THE  AIR  WAVES. 


after  passing  through  the  Antipodes  and  again  returning  through  Krakatoa ;  together 
with  the  deduced  velocities  of  the  wave's  transmission,  are  shown  in  Table  YI. 

TABLE  VI. 

Time  intervals,  and  velocities  between  the  origin  and  jirst  passage  of  the  wave, 
and  between  its  successive  recurrences  travelling  in  the  same  direction. 

The  velocities  are  expressed  in  degrees  of  the  Equator  and  decimals,  per  hour. 


Station. 


Melbourne  •  • 

Sydney 

Danedin      •  • 

Wellington,  N.Z. 

South  ueorgia 

Loanda 

Manritins 

Bombay 

Calcutta 

Zi-Ka-Wei 

Toldo 

Pawlowsk 

St.  Petersburg 

Buda-Pesth 

Vienna 

Berlin 

Leipsic 

Magdeburg . . 

Munich 

Modena 

Rome 

Palermo 

San  Fernando 

Lisbon 

Serra  da  Estrella  . . 

Coimbra 

Paris: — Pare  St.  Maur 

Montsouris 
Brussels 
Greenwich  . . 

Kew 

Oeldeston   . . 

Oxford         

Falmouth    . . 

Valencia 

Armagh 

Liverpool    . . 

Stonyhnrst . . 

Glasgow 

Aberdeen    . . 

Toronto 

New  York  . . 

Hastings-on-Hudson,  N.Y. 

Washington 

Havana 


Between  time  of 

Between 

PMHcee 

Between 

I«MM« 

Between 

PMM«« 

origin  and 

pueagel. 

I.  andlll. 

ULwuiV. 

V.  and  VII. 

Inteiral 

Hourly 
nte. 

InterrmL 

Houriy 
rmte. 

InterraL 

Hourlj 
rate. 

Interna. 

Hourly 

houn. 
4-70 

degree*. 
10- 19 

houn. 
34-97 

degrees. 
10-29 

houn. 

•  • 

degrees. 

houn. 

•  • 

degreet. 

4-87 

10-38 

34-90 

10-32 

36-35 

ib*-i8 

•  • 

e   • 

6-72 

10-19 

35  00 

10-29 

•  • 

, , 

, , 

•   • 

6-80 

10-87 

35  -42 

10-16 

•  • 

•  • 

,  , 

11-87 

9-38 

33-00 

10-91 

•  • 

, , 

•  • 

•  • 

8-77 

10-41 

34-95 

10-30 

85-13 

10-25 

35-00 

10-29 

4-76 

10-21 

34-66 

10-42 

34-58 

10-41 

34-76 

10-36 

3-90 

10-44 

36-57 

9-84 

,  , 

,  , 

•  • 

•  « 

8-25 

10-19 

86-58 

9-84 

,  . 

•  • 

,  , 

3-92 

10-30 

36  45 

10  16 

,  , 

.  • 

,  , 

6-32 

9-90 

35 -36 

10-18 

,  , 

,  , 

,  , 

,  , 

8-77 

10-01 

37-00 

9-73 

36-83 

9-91 

,  , 

8-70 

10-11 

36-42 

9-88 

37-08 

9-71 

,  , 

•  . 

8-97 

10-27 

36-42 

9-88 

36  83 

10-06 

•  • 

,  , 

903 

10-41 

36-58 

9-84 

,  , 

•  • 

•  • 

,  , 

9-83 

10-30 

36-75 

9-80 

86-62 

9-83 

36-38 

9-90 

10-47 

9-23 

•  • 

,  , 

•  • 

•  • 

•  • 

•  • 

9-45 

10-28 

36-48 

9-87 

35  -05 

10-27 

•  • 

•  • 

9-05 

10-73 

36-92 

9-75 

35-60 

10  14 

•  • 

•  • 

9-32 

10-46 

36-33 

9-91 

36-25 

9-93 

86  17 

9-96 

9-47 

10  16 

35-92 

10  02 

•  • 

•  • 

•  • 

,  , 

10-08 

9-46 

•  • 

•  • 

.  , 

,  , 

•  • 

,  , 

9-83 

11-29 

35-88 

10-05- 

,  , 

,  , 

,  , 

10-75 

10-50 

35-92 

10  02 

,  , 

^ 

10-30 

10-82 

36-17 

9-95 

,  , 

•  • 

•  • 

10-80 

10-38 

35-83 

10-06 

•  • 

•  • 

,  , 

10-15 

10  16 

36  33 

9-91 

86-88 

9-77 

,  ^ 

10  03 

10-29 

36-33 

9-91 

•  • 

,  , 

9-93 

10-24 

36-62 

9-83 

86-52 

9-86 

•  • 

,  , 

10-22 

10-21 

36-47 

9-87 

36-82 

9-78 

87-05 

9-72 

10-27 

10  18 

36-40 

9-89 

36-97 

9-74 

37-00 

9-73 

10  12 

10-20 

36-38 

9-90 

36-95 

9-74 

36-58 

9-85 

10-35 

10-15 

36-37 

9-90 

•  • 

,  , 

,, 

•  • 

10-53 

10-23 

36-85 

9-90 

•  • 

,  , 

•  • 

,  , 

10-88 

10-16 

36-43 

9-88 

36-85 

9-77 

•  • 

,  , 

10-72 

10-05 

36-50 

9-86 

36-62 

9-88 

87-13 

9-70 

10-43 

10-15 

86-45 

9-88 

86-92 

9-75 

36-75 

9-80 

10-38 

10  16 

36-53 

9-86 

86-56 

9-86 

37  17 

9-69 

10-60 

10-10 

36-60 

9-84 

36-62 

9-83 

37-08 

9-71 

10-33 

10-12 

36-67 

9-82 

86-67 

9-82 

37-13 

9-70 

14-02 

10-14 

37-75 

9-54 

36-70 

9-81 

35-72 

10  08 

14-36 

10-13 

37-47 

9-61 

•  • 

•  • 

., 

•  • 

14-40 

10-10 

37-75 

9-64 

,  , 

e  • 

•  • 

14-47 

10-17 

37-55 

9-59 

36-68 

9-83 

86  -82 

10-05 

15-47 

10-43 

36-83 

9-7? 

•  • 

•  • 

•  • 

•  • 

The  corresponding  time  intervals  between  the  origin  of  the  wave  and  its  second 
passage  over  the  several  stations,  after  having  travelled  from  Ejrakatoa  through  its 


LIEUT.-GBNERAL  STRACHEY  ON  THE  AIR  WAVES. 


71 


Antipodes;  as  well  as  the  intervals  between  the  successive  subsequent  passages  of  the 
wave,  after  travelling  in  the  same  direction  round  the  earth,  through  Krakatoa,  and 
again  returning  through  its  Antipodes ;  together  with  the  deduced  velocities  of  the 
wave's  motion,  are  shown  in  Table  VII. 

TABLE  VII. 
Time  intervals  and  velocities  between  the  origin  and  second  passage  of  the  wave, 
and  between  its  successive  recurrences  travelling  in  the  same  direction. 

The  velocities  are  expressed  in  degrees  of  the  Equator  and  decimals,  per  hour. 


station. 

Between  time  of  origin  and 
pungell. 

Interval. 

Hoorir  nt». 

InMml. 

Hoorif  ntt«. 

Interm. 

Hoorly  rwe. 

Hoora. 

Degrees. 

Houn. 

I^WrtM. 

Houn. 

Degrees. 

Melbonme 

30-88 

10- 11 

36-26 

10  -21 

*  • 

Dunedin   •  •          .  •          • . 

30-88 

10-19 

35-50 

10-14 

.  • 

28-47 

10-24 

86-00 

10-00 

Wellington,  N.Z. 
South  Georgia 

Loanda     

Maoritins  •  • 
Bombay    . . 
Calcutta    .. 

28-72 
24-28 
27-02 

10-08 

10-24 

9-96 

35-75 
36-18 
36-08 

10-07 
9-95 
9-98 

•  • 

35-76 

•  • 

10*07 

80-97 
30-85 
81-27 

10-06 
10-85 
10-45 

86-17 
35-17 

•  • 

9-95 

10-24 

•  • 

35-25 

•  • 

10-21 

Zi-Ka-Wei 

32-12 

9-95 

•  • 

•  « 

•• 

•  • 

Tokio 

80-80 

9-98 

•  • 

•  • 

Pawlow&lc                           •  • 

25-93 

10-60 

34-42 

10-46 

^     «P  WW  *^^  WW  9^m^                                          •     ■                                •     »                                »     • 

St.  Petersburg 

Buda-Pestli          

25-87 
24-80 

10-62 
10-80 

34-42 
35-83 

10-46 
10-06 

-• 

,  , 

Vienna      • . 

25-62 

10-88 

•  . 

•  • 

•  • 

•  • 

Berlin 

25-08 

10*62 

34-62 

10-40 

•  • 

.. 

Leipsio      •. 
Magdeburg           . , 

26-13 
26  07 
24-97 

10-48 
10-48 
10-53 

34-70 
35-17 

10*87 
10-24 

34-83 

•  • 

10-34 

Modena     • . 

24-73 

10-61 

34-83 

10-49 

34-92 

10-31 

Rome 

25-88 

10-39 

•  • 

•  • 

•  • 

Palermo    •  •       -   . .          •  •          •  • 

25-92 

10-21 

•  • 

Snn  Fernando 

28-47 

10-61 

35-03 

10-28 

TiiaVkOIl          .  .              .  .              •  .             • 

23-76 

10-41 

85-26 

10  21 

Serra  da  Estrella 

23-97 

10-37 

84-50 

10-43 

■  • 

Coimbra   •  • 

Paris  :— Pare  St.  Maur  . . 

23-72 
24-82 

10-45 
10-36 

36-13 
34-72 

10-26 
10-87 

•  • 

•  • 

Montsouris 

Brussels 

Ghreenwich 
Kew 

Geldeston 

Oxford 

Falmouth 

Valencia 

Armagh    . . 
Lirerpool  - . 

Stonyhurst            

Glasgow    . . 

Abei^een 

Toronto     •  •           •  •           •  •           •  * 

24-82 
24-85 

10-35 
10-39 

34"-28 

10*-60 

85-22 

10-22 

24-48 

10-47 

84-78 

10-85 

35  -25 

10-21 

24-55 

10-41 

34-62 

10-40 

86-80 

10-20 

24-57 
24-65 

10-46 
10-39 

84-63 
84-60 

10-40 
10-48 

85-83 

•  • 

10-19 

24-18 

10-43 

84-73 

10-37 

85-55 

10-18 

28-72 

10-62 

34  92 

10-81 

36-06 

10-27 

24-00 

10-61 

34-83 

10-34 

34-75 

10-36 

24  15 

10  62 

34-98 

10-29 

84-50 

10-43 

24-22 
24-22 

10-61 
10-49 

34-83 
34-68 

10-34 
10-38 

34-58 
34-70 

10-41 
10  -37 

24-33 

10-50 

34-67 

10-38 

35-80 

10  OG 

22-27 

9-78 

32  08 

11-22 

38-42 

10-77 

New  York 

21-90 

9-80 

32-87 

10-96 

•  • 

a    • 

Hastings-on-Hudson,  N.Y. 

21-90 

9-80 

32-83 

10-97 

/   32*63 
lor  33 -28 

li-07 

Washington         

21-80 

9-76 

32  52 

11-07 

or  10  -82 

Havana     

20-72 

9-69 

32-75 

10-99 

•• 

•• 

L  2 

72  LIEUT.-GENBRAL  STELiOHBT  ON  THE  AIR  WAVBS. 

The  velocities  of  the  wave  thus  obtained  will  be  seen  to  range  from  about  ^^'7i 
per  hour  to  lO'^^  per  hour,  or  from  674  to  726  English  miles  per  hour.  The  velocity  of 
sound  in  air,  of  a  temperature  of  50°  Fahrenheit, is  757  miles  per  hour, and  at  80°  Fahren- 
heit it  is  781  mDes;  at  a  temperature  of  zero  Fahrenheit  it  is  reduced  to  723  miles 
per  hour.  Thus  it  appears  that  the  atmospheric  disturbance  now  in  question  had  very 
nearly  the  characteristic  velocity  of  sound,  and  that  its  mode  of  propagation  by  an 
aerial  oscillation,  of  comparatively  short  duration,  was  also  closely  analogous  to  that 
of  sound.  Moreover,  although  there  is  no  direct  evidence  that  the  great  final 
explosion,  which  produced  this  atmospheric  disturbance,  was  accompanied  by  sounds 
heard  at  any  considerable  distance,  it  is  well  established  that  during  the  progress  of 
the  eruption  the  sounds  of  some  of  the  explosions  were  heard  at  very  great  distances ; 
certainly  at  Ceylon,  about  2,000  English  miles  from  the  volcano,  and  at  many  places 
between  1,000  and  1,500  miles  distant;  and  probably  at  Bodriguez,  about  3,000 
English  miles  distant.  Further  details  on  this  subject  will  be  found  in  the  subsequent 
section  upon  Sounds. 

The  results  given  in  Tables  YI.  and  VII,,  when  examined  more  closely,  indicate 
that  there  were  sensible  variations  in  the  velocity  of  the  wave's  transmission  in  the 
same  direction  over  the  various  stations,  and  that  the  velocity  of  the  waves  moving 
in  different  directions  over  the  earth's  surface  likewise  diflPered  considerably.  Some  of 
the  apparent  variation  is,  no  doubt,  due  to  the  imperfection  of  the  data,  and  the 
difficulty  before  mentioned  of  identifying  the  standard  phase  of  the  wave,  on  the 
moment  of  the  occurrence  of  which  such  calculations  as  these  must  be  based.  But 
the  differences  are  too  great  and  too  consistent  to  be  entirely,  or  even  mainly,  attri- 
buted to  these  causes. 

This  will  be  made  apparent  from  the  following  considerations.  The  velocity  of 
the  wave,  in  degrees  per  hour,  in  passing  round  the  earth,  is  360^  divided  by  the  time 
of  transit.  If  this  time  be  assumed  to  be  approximately  36  hours,  and  the  variation 
from  it,  whether  positive  or  negative,  be  called  x,  in  hours,  the  velocity  will   be 

o^^   =10°— y,  where  y  is  the  corresponding  variation   of   the   velocity  from    10° 

lOx 
per  hour.     Consequently,  y=Q^  ■     >  and  hence  an  error  of  10   mins.   in  the  time 

would  produce  a  change  in  the  deduced  velocity  of  only  0°*046  per  hour,  and 
an  error  of  half  an  hour  would  change  the  velocity  by  only  0°137  per  hour. 
The  probable  limits  of  error  in  the  estimation  of  the  times  are,  in  almost  all 
cases,  well  within  thirty  minutes,  and  the  few  exceptions  that  are  found  have  no 
practical  influence  on  the  general  conclusions  adopted. 

It  will  be  seen  that  there  is  great  general  similarity  in  the  respective  time 
intervals  and  velocities  for  the  whole  series  of  stations,  comprised  in  the  two  tables 
between  Pawlowsk  and  Aberdeen,  which  includes  all  the  European  stations  on 
which   the   most  confidence  can   be  placed.      The   paths   of   the  portions  of   the 


LIEUT.-GBNERAL  STRACHEY   ON  THE  AIR  WAVES.  73 

wave  that  passed  over  these  places  do  not  vary  greatly  in  azimuth,  and,  pre- 
sumably, the  general  conditions  of  temperature  also  will  not  have  varied  greatly 
among  them. 

Now,  from  Table  VI.  it  will  be  found  that  the  mean  velocity  of  the  wave  for 
twenty-nine  of  these  stations,  in  passing  for  the  first  time  from  Krakatoa  to  them,  is 
10°'23  per  hour.  The  average  velocity  in  the  same  dii-ection  between  the  first  and 
third  passages,  over  twenty-seven  of  the  same  stations,  during  which  the  wave  com- 
pleted the  circuit  of  the  earth,  was  reduced  to  9°'89  per  hour  ;  the  mean  time 
occupied  in  the  passage  being  36  hrs.  24  mins.  For  the  next  passage  round  the 
earth  the  mean  velocity  for  eighteen  of  the  stations  was  9°*86  per  hour,  and  the  time 
occupied  36  hrs.  30  mins. ;  while,  for  the  last  observed  passage  over  ten  stations 
the  mean  velocity  was  9°77  per  hour,  and.  the  period  which  elapsed  was  36  hrs. 
50  mins. 

The  corresponding  quantities  for  the  alternate  passages  of  the  wave,  extracted 
from  Table  VII.,  are  as  follows  : — The  mean  velocity  of  the  wave,  while  travelling  from 
Krakatoa  through  its  Antipodes,  to  the  same  twenty-nine  stations  as  before  dealt 
with,  is  10^*47  per  hour  ;  for  twenty-four  stations  the  mean  velocity  between  the  second 
and  fourth  passages,  during  which  also  the  circuit  of  the  earth  was  completed,  is  10*^*3  5 
per  hour,  the  mean  time  occupied  being  34  hrs.  46  mins. ;  while,  for  the  next  passage, 
which  is  also  the  last  observed  in  this  direction,  thirteen  stations  give  a  mean  velocity 
of  10°'27  per  hour,  with  a  period  of  transit  of  35  hrs.  4  mins. 

It  will  further  be  seen  that  the  velocities  derived  from  the  observations  at 
Calcutta  and  Bombay,  which  lie  within  the  zone  traversed  by  the  portion  of  the  wave 
that  passed  over  the  European  stations,  correspond  generally  in  character  with  those 
that  have  just  been  described,  and  that  the  reduction  of  the  velocity  between  the  first 
and  third  passages  was  almost  the  same. 

On  the  other  hand,  at  the  Australian  and  New  Zealand  stations  which  lie  within 
the  same  zone  of  the  earth's  surface,  but  to  the  eastward  of  Krakatoa,  and  over  which, 
therefore,  the  movements  of  the  several  passages  of  the  wave  were  in  almost  directly 
opposite  directions  to  those  over  the  European  stations,  the  velocity  between  the  first 
and  third  passages  hardly  differs  from  that  between  the  origin  and  the  first  passage, 
in  both  which  the  motion  of  the  wave  was  ivith  the  earth's  rotation  ;  while  between 
the  origin  and  the  second  passage,  as  well  as  between  the  second  and  fourth  passages, 
during  which  the  wave  travelled  round  the  earth  against  the  direction  of  rotation,  the 
velocity  is  sensibly  less  than  that  observed  over  the  European  stations,  where,  between 
the  same  passages  of  tlie  wave,  its  motion  was  in  the  opposite  direction. 

The  difference  of  the  velocities  of  the  waves  that  travelled  with  and  against  the 
direction  of  the  earth's  rotation  amounts  to  about  four-tenths  of  a  degree,  or  28  English 
miles  per  hour,  and  it  may  probably  be  accounted  for  by  the  circmnstance  that  the 
winds  along  the  paths  of  this  portion  of  the  wave  would,  on  the  whole,  have  been 
westerly,  which  would  have  caused  an  increase  of  velocity  in  the  wave  moving  with  the 


74  LIEUT..GBNBRAL  STRACHEr  ON  THE  AIR  WAVES. 

earth's  rotation,  and  an  equal  diminution  in  that  moving  in  the  opposite  direction,  so 
that  the  observed  difference  of  28  miles  could  be  produced  by  an  average  westerly 
current  of  14  miles  per  hour,  which  is  not  imlikely. 

There  is  some  appearance  of  a  greater  retardation  of  the  wave  in  passing  in  a 
direction  opposed  to  the  earth's  rotation  over  the  northern  European  stations  as  com- 
pared with  those  in  the  south  of  Europe,  which  may  possibly  be  due  to  the  lower 
temperature  of  the  more  northern  part  of  the  zone  traversed.  This  difference  is  not 
to  be  traced  in  the  wave  n\oving  in  the  opposite  direction,  which  may  be  accounted  for 
by  the  path  of  the  wave,  when  approaching  Europe  from  the  vest,  having  lain  for  a 
long  distance  over  the  Atlantic,  where  the  differences  of  temperature  between  the 
northern  and  the  southern  borders  of  the  zone  traversed  would  have  been  relatively 
small. 

The  velocities  observed  at  Mauritius  and  Loanda,  the  paths  of  the  waves  passing 
over  which  lie  respectively  within  20°  and  10®  of  the  Equator,  are  very  nearly  alike ; 
the  wave  travelling  to  the  west  not  being  sensibly  retarded,  while  that  travelling  to 
the  east  is  so  retarded.  This  may  be  caused  by  the  paths  pf  the  waves  falling  entirely 
within  the  zone  of  the  Trade  Winds,  which  both  north  and  south  of  the  Equator  blow 
from  the  east,  and  would  therefore  cause  a  relative  retardation  of  the  wave  travelling 
with  the  earth's  rotation. 

The  path  of  the  wave  that  passed  over  the  Canadian  and  United  States  stations, 
and  Havana,  lies  nearly  on  the  meridian  drawn  through  Krakatoa,  and  must  have 
crossed  both  the  polar  circles  very  near  the  poles.  The  velocities  obtained  from  these 
stations  are  peculiar.  The  dbect  wave  from  Krakatoa,  which  travelled  nearly  due 
north  and  close  to  the  north  pole«  and  its  repetitions  after  passing  round  the  earth  in 
the  same  direction,  had  nearly  the  same  velocities  as  those  observed  at  the  European 
stations,  with  an  apparent  decided  retardation  in  the  intervals  between  the  first  and 
third  passages,  and  (but  to  a  less  extent)  between  the  third  and  fifth.  The  wave 
that  passed  through  the  Antipodes  before  reaching  the  North  American  stations  went 
nearly  due  south,  close  to  the  south  pole ;  and  its  velocity  on  this  its  first  partial 
passage  round  the  earth  was  very  decidedly  reduced ;  but  in  its  next  complete  circuit, 
that  between  the  second  and  fourth  passages  over  the  stations  of  North  America^  the 
velocity  appears  to  have  been  much  increased,  almost  reaching  the  full  rate  of  the 
true  sound-wave.  It  is  difficult  to  account  for  this,  but  the  fact  seems  to  be  indis- 
putable. 

The  peculiarities  affecting  the  velocity  of  the  waves  will  be  subsequently  again 
referred  to ;  and  diagrams  are  given  which  show  graphically  the  manner  of  their 
occimrence,  and  supply  further  evidence  of  the  truth  of  the  conclusions  that  have  now 
been  stated. 

The  variations  of  velocity  in  the  waves  moving  in  opposite  directions  are  clearly 
shown  by  the  following  Table  VIII.,  which  gives  the  time  intervals  between  the 
passage  of  the  successive  waves,  irrespective  of  their  direction.     When   the   time 


LIEUT.-GBNERAL  STRACHEY  ON  THE  AIR  WAVES. 


75 


interviews  increase,  either  the  first,  third,  and  fifth  passages  are  accelerated,  or  the 
second,  fourth,  and  sixth  are  retarded  ;  and  when  the  intervals  diminish,  the  converse 
holds  good. 


TABLE   VIII. 

Time  intervals  between  the  passages  of  the  successive  waves,  irrespective  of 
their  direction. 


Interval  between  Passages. 

fifft'fioTl 

Kj  %ftm  VA\ja  • 

I.- 

II. 

II.- 

III. 

iii-rv. 

IV.-V. 

V.- 

VI. 

VI.-VII. 

hr. 

min. 

hr. 

min. 

ht.  min. 

hr.  min. 

hr. 

min. 

hr.  min. 

Pawlowsk 

17 

10 

19 

50 

14    36 

21     45 

St.  Petersburg 

17 

10 

19 

16 

16     10 

21     56 

Aberdeen  . . 

U 

0 

22 

40 

12       0 

24    40 

11 

8 

26      0 

Glasgow 

13 

43 

22 

53 

11    48 

24    49 

9 

63 

27    12 

Armagh    • . 

13 

17 

23 

13 

11     37 

25      0 

9 

46 

27    23 

Stonyhnrst 

13 

60 

22 

42 

12      8 

24    25 

10 

10 

27      0 

Liverpool  •  • 

13 

43 

22 

44 

12     15 

24    40 

9 

60 

26    66 

Berlin 

15 

45 

21 

0 

13    37 

23      0 

Geldeston 

14 

27 

21 

56 

12    42 

24    15 

11 

5 

26    27 

Magdeburg                                  . . 

15 

37 

20 

62 

J3    60 

21     13 

13 

37 

Valencia  . . 

12 

60 

23 

30 

11     19 

25    32 

U 

31 

Oxford 

14 

12 

22 

10 

12    20 

Greenwich 

14 

13 

22 

15 

12    32 

24    17 

10 

68 

26      6 

Kew          

14 

17 

22 

7 

12    30 

24    28 

10 

50 

26    10 

Leipsic 

14 

40 

Bmssels 

14 

65 

21 

42 

12    35 

23    56 

11 

17 

Falmonth . . 

13 

39 

22 

42 

12      2 

Paris- 

Fare  St.  Maar 

14 

40 

21 

40 

13      3 

23    47 

Montsonris   . . 

14 

47 

21 

33 

Vienna 

16 

35 

20 

0 

Munich     . . 

15 

56 

21 

0 

14    10 

21    20 

Buda-Pesth          

15 

50 

20 

35 

15    15 

20    35 

Modena    . . 

15 

25 

20 

65 

13    26 

22    50 

12 

5 

24      6 

Rome 

15 

55 

20 

0 

Serrs  da  Estrella 

13 

40 

22 

30 

12      0 

Coimbra  . . 

12 

55 

22 

55 

12    13 

Lisbon 

13 

0 

22 

65 

12    20 

Palermo    . . 

15 

50 

San  Fernando                  .-. 

13 

38 

22 

12 

12    50 

Mean 

14 

41 

21 

46 

12    61 

23    28 

10 

61 

26    15 

Calcutta 

28 

1 

8 

34 

Bombay 

26 

57 

9 

87 

25    33 

Mean     . . 

27 

29 

9 

6 

26    33 

7G 


LTEUT.-GENERAL   STRACHEY  ON  THE  AIR    WAVES. 


Table  VIII. — continued. 


Station. 


Interval  between  Passages. 


I.-II.  II.-III. 


III.-IV.       IV.-V. 


V.-VI. 


vi.-vn. 


Manritius . . 
Loanda      • . 


Mean 


Dunedin   .  • 
Wellington,  N.Z... 

Mean     . 

Mcll5bume 
Sydney 

Mean     . 
South  Georgia     .. 


Tokio 
Zi-Ka-Wei 

Mean 


Toronto     . . 
New  York 
Hastings-on-Hudson,  N.Y 

Washington 


Mean 


Havana. . 


hr.  min. 
26     13 
i     18     15 


2'2 

14 

21 
21 

45 
55 

21 

50 

26 
25 

11 
31 

25 

51 

12 

26 

25 
28 

29 
12 

26 

5] 

8  15 

7  33 

7  30 

7  20 


7    40 


5     15 


hr.  min.       hr.  min. 

8    20         27     50 

16    42     !     19     23 


12 

31 

13 
13 

15 
30 

13 

23 

8 
9 

47 
23 

9 

5 

20 

35 

9 

7 

52 
15 

8 

34 

30     13 


29    58 


31     35 


23 

37 

22 
22 

45 
15 

22 

30 

26 
26 

28 

7 

26 

18 

15 

36 

29 

30 

2 

35 

29 

55 

2 

57 

30 

15 

2 

36 

2    18 


2    36 


1     10 


hr.  min. 

6     45 

15    45 

11     15 


9     14 
9     14 


34       7 


34    20 


34    14 


hr.  min. 
28     30 
20      0 

24     15 


*0    42 


•1      3 
or 
1     48 


0 

63 

or 

1 

15 

hr.  min. 

6     15 

15       0 

10     38 


36     25 


36  52 
or 

37  37 

36  39 
or 

37  1 


•  The  order  of  the  waves  had  been  reversed  here,  so  that  the  sixth  wave  arrived  before  the  fifth. 


From  a  comparison  of  twenty -four  European  stations,  it  appears  that  the  mean 
interval  between  the  second  and  first  passages  is  greater  than  that  between  the  fourth 
and  third  passages  by  2  hours  ;  and,  similarly,  for  twelve  stations  the  mean  of  the 
first  of  these  intervals  is  greater,  by  3  hrs.  40  mins.,  than  the  mean  interval  between  the 
sixth  and  fifth  passages.     At  two  of  the  American  stations,  Toronto  and  Washington, 


LIEUT.-GBNERAL  STRACHEY  ON  THE  ATB  WAVES.  77 

the  mean  interval  between  the  first  two  passages  of  the  wave  exceeded  that 
between  the  second  pair  by  5  hrs.  22  mins.,  and  the  first  of  these  intervals  exceeded 
that  between  the  smaller  mean  of  the  third  pair  of  passages  by  8  hrs.  41  mins.  The 
result  of  this  great  variation  in  the  velocity  of  the  waves  was  that  at  last  the  two 
waves  from  the  opposite  directions  became  confused,  and  must  have  crossed  each  other; 
and  some  doubt  therefore  exists  as  to  the  precise  time  that  should  be  assigned  to  their 
respective  passages. 

In  order  to  illustrate  the  manner  in  which  the  disturbance  travelled  round  the 
earth,  a  series  of  projections,  Plates  X.,  XL,  XII.,  and  XIII.,  have  been  prepared,  on 
which  the  position  of  the  wave  is  marked  for  each  successive  even  hour  of  Greenwich 
mean  time,  beginning  with  4  hrs.  of  August  27th,  civil  reckoning,  till  its  traces  were 
lt)st.  The  projection  or  development,  which  is  quite  coiiventional,  shows  Krakatoa 
and  its  Antipodes  in  the  centres  of  two  circles,  representing  the  two  hemispheres,  of 
which  those  points  are  the  poles.  The  geographical  features  of  the  earth  are  projected 
on  the  hypothesis  that  distances  from  the  centres  of  the  two  circles  are  the  distances 
of  the  points  to  be  represented,  measured  over  the  earth's  surface  on  the  arc  of  a  great 
circle,  from  Krakatoa  or  from  its  Antipodes,  as  the  case  may  be.  The  diameters  of 
the  circles  represent  great  circles  passing  through  Krakatoa,  and  therefore  indicate 
the  paths  of  the  various  points  of  the  wave  as  it  advanced. 

The  wave  of  atmospheric  disturbance,  if  it  had  been  propagated  without  intet- 
ference,  would  have  spread  outwards  from  Krakatoa,  in  a  gradually  expanding  small 
circle,  until  it  reached  a  distance  of  90°  from  its  origin,  and  thus  have  formed  a  great 
circle ;  beyond  which  it  would  have  contracted  as  it  advanced,  till  it  once  more 
coalesced  into  a  point  or  focus  at  the  Antipodes.  Thence  it  would  return  in  like  manner, 
and  again  be  concentrated  at  its  starting  point ;  and  so  on,  until  it  gradually  died  out. 
The  departure  of  the  curved  lines  (which  represent  the  successive  positions  of  the 
wave)  from  a  true  circular  form,  indicates  the  irregularity  in  the  velocity  of  the  various 
points  of  the  wave's  front,  and  the  distortion  naturally  increases  gradually  with  the 
prolonged  duration  of  the  wave's  progress. 

The  phenomena  are  otherwise  represented  in  Plates  XIV.  and  XV.,  which  show 
more  clearly  the  variation  of  the  velocities  of  the  wave's  movement  over  the  several 
stations,  and  contrast  the  velocities  of  the  motion  in  directions  which  may  be  spoken 
of,  in  geperal  terms,  as  being  in  conformity  with,  or  in  opposition  to,  that  of  the 
earth's  rotation. 

In  these  two  plates  the  time-intervals  are  represented  by  the  ordinates,  or 
vertical  distances  from  the  base  line,  which  corresponds  with  the  assumed  origin  of 
the  reckoning,  viz.,  0  hrs.  of  August  27th,  G.M.T.,  civil  reckoning.  The  distances 
of  the  several  stations  from  Krakatoa,  as  measured  on  arcs  of  great  circles,  are  the 
abscissse  or  horizontal  distances  from  the  central  line,  supposed  to  represent  the 
origin  of  the  wave  ;  those  on  the  right  of  the  central  line,  Plate  XV.,  being  the  dis- 
tances measured  to  the  westward,  or  against  the  earth's  rotation  ;  those  on  the  left', 

M 


78  LIEUT.-GENERAL  STRACHEY  ON  THE  SOUNDS. 

Plate  XIV.,  being  the  distanceB  measured  in  the  opposite  direction.  An  addition  of 
360^  is  made  for  each  complete  passage  of  the  wave  round  the  earth. 

The  inclined  lines  drawn  through  the  point  where  the  central  line  cuts  the 
assumed  moment  of  the  origin  of  the  wave,  and  the  points  on  the  proper  ordinates 
which  represent  the  time  of  passage  of  the  wave  at  the  several  stations,  indicate  the 
Velocity  of  the  wave's  transmission ;  an  increased  inclination  showing  reduced  velocity, 
and  the  converse.  To  distinguish  between  the  waves  that  passed  over  different  places, 
the  lines  of  velocity  are  differently  drawn,  as  is  explained  on  the  Plate  itself. 

The  retardation  of  that  portion  of  the  wave  which  travelled  by  way  of  the  South 
Pole  to  the  North  American  stations,  already  referred  to  on  page  74,  is  very  well 
shown  by  the  diagram,  Plate  XIV.,  illustrating  the  progress  of  the  wave  travelling 
with  the  earth's  rotation.  The  line  drawn  from  Krakatoa  to  Toronto  has  at  first  a 
greater  inclination  than  any  other  line,  indicating  that  the  velocity  of  the  wave  was, 
in  this  part  of  its  course,  the  least  of  all ;  but  afterwards  the  inclination  becomes 
less  than  that  of  any  other  line,  showing  that  the  velocity  of  the  wave  had  changed 
and  become  the  greatest  of  all. 

The  observations  at  South  Georgia,  which,  speaking  in  a  general  manner,  lies  in 
the  same  track,  confirm  those  at  the  American  stations ;  and  indeed  it  seems  that  the 
greatest  retardation  took  place  in  the  Southern  Ocean,  since  (as  the  diagram  will 
show),  the  inclination  of  the  velocity  line  would  have  had  to  be  still  further  increased 
to  make  it  pass  exactly  through  the  point  representing  South  Georgia. 

Probably  an  explanation  of  this  peculiar  feature  of  the  phenomena  may  be  found 
in  the  conditions  of  the  wind  and  weather  in  the  Southern  Ocean,  during  the  days  on 
which  the  wave  passed  over  it,  which  are  not  known  to  us. 


Section  II.— SOUNDS. 


In  Table  IX.,  p.  80,  will  be  found  a  list  of  places  at  which  the  sounds  of  the 
explosions  were  heard ;  and  although  the  list  is  not  a  complete  one,  it  is  as  nearly 
so  as  it  was  possible  to  make  it  with  the  information  available.  The  repetition, 
howevw,  of  places  comparatively  close  to  the  Strait  of  Sunda  could  have  given  but 
little  additional  value  to  the  list,  which,  as  it  stands,  contains  all  the  more  distant 
places  at  which  it  has  been  reported  that  the  sounds  were  heard. 

No  sounds  were  heard  before  the  26th ;  and  all  the  reports  agree  that  the  most 
violent  detonations  occurred  on  the  morning  of  the  27th.     Owing,  however,  to  the 


LIEUT.-GBNERAL  STRACHEY  ON  THE  SOUNDS.  W 

great  uncertainty  which  is  attached  to  the  times  at  which  it  is  stated  that  the  sounds 
were  heard — from  the  somewhat  general  way  in  which  they  are  sometimes  given,  e,g.^ 
'^^t  about  10  a.m.,"  or  *' between  9  and  10  a.m./'  &c.,  the  unreliability  of  the  clocks, 
or  from  other  causes — the  exact  times  at  which  the  explosions  occurred  cannot  safely 
be  deduced  from  them  ;  although,  as  far  as  they  bear  upon  the  conclusions  already 
deduced  from  other  sources  as  to  the  time  of  origin  of  the  great  air-wave^  so  far  from 
their  being  opposed  to  those  conclusions  they  appear  to  support  them  fairly  welL 

The  sounds  were  heard  with  great  distinctness  over  the  most  distant  parts  of 
Java  and  Sumatra  throughout  the  morning  of  the  27th,  but  it  is  very  remarkable  that 
at  many  places  in  the  more  immediate  neighbourhood  of  the  volcano  they  ceased  to  be 
heard  soon  after  10  a.m.,  although  it  is  known  that  the  explosions  continued  with 
great  intensity  for  some  time  longer.  Very  probably  this  peculiar  phenomenon  was 
caused  by  the  large  amount  of  solid  matter  which  at  about  that  time  (10  a,ra,  local 
time)  was  ejected  into  the  atmosphere  by  the  volcano,  and  which  formed  in  the  lower 
strata  of  the  air  a  screen  of  suflBcient  density  to  prevent  the  sound  waves  from 
penetrating  to  those  places  over  which  it  was  more  immediately  suspended. 

The  principal  places  mentioned  in  the  Table  have  been  marked  upon  Plate  XVI., 
which  is  a  map  constructed  upon  a  projection  similar  to  that  used  for  showing  the 
progress  of  the  air-wave,  and  having  Krakatoa  as  its  centre. 

Small  circles  have  been  drawn  upon  this  map  with  radii  of  10"^,  20^. , . ,  50^  ■  and 
it  will  be  seen  that  the  30°  line  is  touched,  or  closely  approached,  by  places  almost 
entirely  surrounding  Krakatoa ;  viz.,  Ceylon  to  the  north-west,  Perth  and  other 
stations  in  West  and  South  Australia  to  the  south-east.  New  Guinea  to  the  east, 
and  Manila  to  the  north-east.  •  Diego  Garcia,  in  the  Chagos  Group,  almost  due  west 
of  Krakatoa,  and  Alice  Springs,  in  South  Australia,  are  beyond  the  30''  line  ;  while 
Rodriguez,  to  the  south-west  of  Krakatoa,  still  more  remote,  lies  beyond  the  40^  line* 
The  shaded  portion  of  the  map  represents  approximately  the  area  over  which  the 
sounds  of  the  explosions  were  heard,  and  is  roughly  equal  to  rather  less  than  one- 
thirteenth  of  the  entire  surface  of  the  globe. 

A  special  interest  is  attached  to  the  report  from  Rodriguez,  owing  to  the 
fiict  that  it  is  not  only  the  most  remote  place  at  which  the  sounds  of  the  explosions 
were  heard,  being  very  nearly  3,000  English  miles  from  Krakatoa,  but  that  it  is 
also  the  only  instance  on  record  of  sounds  having  been  heard  at  anything  like 
so  great  a  distance  from  the  place  of  their  origin.  It  may,  therefore,  be  well  to 
quote  here  the  account  given  by  Mr.  James  Wallis,  Chief  OflScer  of  Police,  who  is 
responsible  for  the  following  narration  : — 

"  On  Sunday  the  26th  the  weather  was  stormy,  with  heavy  rain  and  squalls  ; 
the  wind  was  from  S.E.,  blowing  with  a  force  of  from  7  to  10,  Beaufort  scale. 
Several  times  during  the  night  (26th — 27th)  reports  were  heard  coming  from  the 
eastward,  like  the  distant  roars  of  heavy  guns.     These  reports  continued  at  intervals 

M  2 


80 


LIEUT.-GENERAL  STRACHET  ON  THE  SOUNDS. 


of  between  three  and  four  hours,  until  3  p.m.  on  the  27th,  and  the  last  two  were 
heard  in  the  directions  of  Oyster  Bay  and  Port  Mathurie." 

At  Diego  Garcia,  upwards  of  2,250  English  miles  from  Krakatoa,  the  sounds 
were  very  distinctly  heard,  and  were  supposed  to  be  those  of  guns  fired  by  a  vessel 
in  distress  ;  a  belief  which  likewise  prevailed  at  Port  Blair  in  the  Andaman  Islands, 
and  at  several  places  less  remote  from  Krakatoa.  In  Ceylon,  and  also  in  Australia, 
the  sounds  were  heard  at  many  diflTerent  places  fer  removed  from  each  other ;  while 
at  Dorey,  in  New  Guinea,  they  were  clearly  heard,  and  their  occurrence  was  recorded 
at  the  time,  long  before  it  was  known  to  what  cause  they  were  due.  These 
circumstances  are  of  value  as  confirmatory  evidence  of  the  sounds  having  been  really 
heard  at  those  distant  places. 

That  the  detonations  were  heard  so  much  further  to  the  westward  than  they 
appear  to  have  been  to  the  eastward  of  Krakatoa,  was  most  probably  due  to  the 
westward  motion  of  the  lower  strata  of  the  atmosphere  in  tlie  region  of  the  Trades, 
within  which  the  most  distant  station,  Rodriguez,  lies. 

It  may  be  noticed  also  that  a  communication  was  made  to  the  "  Academic  des 
Sciences,"  and  published  in  the  Comptes  Rendus  in  March,  1885  (vol.  c,  p.  755), 
giving  an  account  of  sounds  said  to  have  been  heard  in  the  Cayman  Islands  in 
Lat.  20^  N.  Long.  80°  W.  from  Greenwich,  South  of  Cuba,  on  August  26th,  1883, 
which  were*  attributed  to  the  eruption  at  Krakatoa.  The  evidence,  however,  is  of 
so  indefinite  a  nature  that  it  has  not  been  inserted  in  the  tabular  statement  annexed. 


TABLE  IX. 

List  of  Places  at  which  the  Sounds  of  the  Explosions  at  Krakatoa  were  heard 
on  the  26th  and  27th  of  August,  1883. 


Placb. 

Distance  from 

KrakatoA, 

in  English  miles. 

Notes. 

JAVA. 

Anjer  . .              .  • 

31 

Tiie  sounds  of  the  explosions  were  heard  from  the 
afternoon  of  the  26th. 

Memk 

38 

''  At  7  p.ni.  26th,  heavy  detonations  and  violent 
shocks,  but  no  earthquake." 

St.  Nicholas  Point 

44 

Sounds  heard  on  26th  and  27th, 

Chikandie  Udik 

62 

"The  reports  grew  louder  and  louder,  until  the 
gronnd  shook  sensibly.  When  evening  set  in 
(26th),  the  detonations,  far  from  diminishing, 
increased  in  violence."  Report  by  an  English 
resident. 

Batavia   ..         ..         .. 

94 

"  On  26th,  about  4  p.m.,  a  series  of  detonations  was 
heard;  towards  night  they  grew  louder;  till  in 
the  early  morning  the  reports  and  concussions 
were  simply  de«3ening."  Report  by  Lloyd's 
agent  at  Batavia. 

LIBUT.-GBNBRAL  STRACHBY  OX  THE  SOUNDS, 
.Table  IX. — continued. 


81 


Place. 


Serang     . . 
Baitenzorg 


Samarang 
Caiimon  Java  Island 


Near  Toelong  Agong,  100  miles 
from  Soarabaja. 


Sonrabaya  (also  on  board  the 
Sea  Witch,  ashore  in  the  bay). 


Distance  from 

Krakatos, 

in  English  miles. 


Notes. 


Probolingo 

Banjos  Wangi,  Straitg  of  Bali 

Yngya  Karta 

SUMATRA. 

TelokBetong 

Katimbang,  north-east  coast  of 
Snnda  Strait. 

Palembang 

Siak         

Dell  •    .       • 

Acheen    •  • 

Eotta  Radja 

Padang   . . 


Bencoolen 
Krod        • . 


48 
100 

346 
355 

About  400  (?) 
507 


542 
616 
357 


44 
24 


228 


519 

818 
1,073 

931 

512 


277 
134 


The  loudest  sounds  were  heard  shortly  after  10  a.m. 
on  the  27th.  .  . 

A  low  rumbling  sound  heard  at  1  p.m.,  26th,  in- 
creasing  in  intensity  soon  afterwards,  and  con- 
tinuing all  through  the  night,  with  occasional 
"violent  explosions. 

Sounds  were  heard  from  the  evening  of  the  26th 
till  the  afternoon  of  the  27th. 

Under  the  belief  that  a  vessel  was  in  distress,  several 
native  boats  were  despatched  to  render  assistanc^b 
on  the  evening  of  the  26th. 

"  The  noise  sounded  like  great  guns  being  fired  at 
irregular  intervals,  and  it  continued  all  through 
the  night,  26th-27th."  Extract  from  letter  of 
Mr.  Edward  St.  George. 

The  detonations  were  heard  on  the  26th  and  27th 
so  distinctly  that  it  appeared  impossible  they 
could  have  come  from  such  a  distance  as 
Krakatoa. 

The  sounds  were  heard  on  the  26th  and  27th. 

The  soands  were  heard  on  the  26th  and  27th. 


The  loudest  report  was  at  about  10  a.m.,  27th. 

"When  it  had  become  quite  ^ark  on  the  26th, 
fearful  detonations  were  heard,  like  thunder  and 
reports  of  guns."  The  loudest  report  was  heard 
at  about  10  a.m.  on  27th. 

The  atrial  vibrations  were  so  strong  as  to  cause  the 
walls  of  houses  to  shake.  The  soands  were 
heard  from  the  aflernoon  of  the  26th  till  the 
morning  of  the  27th. 

The  sounds  were  heard  from  the  afternoon  of  the 
26th  till  11  a.m.  27th.  ' 

The  sounds  were  heard  on  the  26th  and  27th. 

It  was  supposed  that  a  fort  was  being  attacked,  and, 
in  consequence,  the  troops  were  put  under  arms. 

The  sounds,  were  not  heard  after  the  night  of  the 
26th-27th. 

*'  At  8.30  a.m.,  27th,  a  heavy  explosion,  repeated 
five  minutes  afterwards.  ....  During  aU  this 
time  a  fearful  noise  was  heard  from  afar,  which 
became  stronger  after  11  a.m."  The  soun^:^ 
were  first  heard  at  5  p.m.  26th. 

The  sounds  were  heard  from  the  afternoon  of  the  26th. 

The  sounds  were  heard  on  the  26th  and  27th.  A 
report  was  heard  on  the  morning  of  the  28th  also. 


82 


LIEUT.-GBNERAL  STRACHET  ON   THE  SOUNDS. 
.Table  IX. — continiied. 


Place. 


BANCA. 


Minto 


Lepa  Island 


BILLITON. 
Tanjong  Pandang 

STRAITS  SETTLEMENTS. 
Singapore 


Distance  from 

Krakatoa, 

in  English  miles. 


284 


242 


277  (abottt) 


522 


Selangore 


Perak 


Penong 


8IAM. 


Bangkok. 


COCHIN  CHINA. 

Cape  St.  Jame8,10*  19' N.,  107' 
6'E. 

Saigon     , 


715 

770 

868 

1,413 

1,138 
1,164 


Notes. 


The   detonations    were    most   violent  during   the 
night  of  the  26th. 

The  loudest  reports  were  heard  near  mid-day  on 
the  27th.  It  was  thought  that  a  vessel  was  in 
distress. 


Loudest  shortly  before  noon  on  the  27th. 


Two  steamers  were  sent  on  the  27th  to  look  for  the 
vessel  which  was  supposed  to  be  firing  guns  as 
signals  of  distress. 

"  Till  3  p.m.  on  Monday,  the  27th,  conversation  was 
utterly  impossible  on  the  Ishore  telephone  line. 
On  raising  the  tubes  a  perfect  roar,  as  of  a 
waterfall,  was  heard,  and  by  shouting  at  the  top 
of  one's  voice  the  clerk  at  the  other  end  heard 
the  voice,  but  not  one  single  sentence  was  under- 
stood. The  same  noise,  but  to  a  less  extent,  was 
noticed  on  eveiy  line  here,  and  sometimes,  while 
listening  to  the  Ishore  line  instruments,  a  report 
like  a  pistol  was  heard."  (The  telephone  line 
crosses  the  strait  between  Singapore  and  Ishore 
by  a  short  cable  about  one  soile  in  length.) 

The  sounds  were  heard  from  4.30  p.m.  26th  till 
5  p.m.  27th. 

The  sounds  were  thought  to  be  distant  salvos  of 
artillery.  Reports  were  heard  on  the  26th  and 
27th. 

At  11  a.m.  27th  the  sounds  were  mistaken  for  a  salute 
from  an  American  corvette,  which,  however,  had 
sailed  four  hours  previously. 


The  reports  were  heard  on  the  27th,  and  are  also 
said  to  have  been  heard  100  miles  in  the  interior. 


The  sounds  were  heard  on  the  27th. 


The  sounds  were  heard  on  the  27th 


LIEUT-GENERAL  STRACHET  ON  THE   SOUNDS. 
Table  IX. — continued. 


83 


Place. 


Distance  from 

Krakatoa, 

in  English  miles. 


Notes. 


BORNEO 
Martapoera 

Bandjermasin     . . 

Jampaga  •  • 

Soekadana 

Pontianak 

Labuan    • . 

Bangaej  Island. . 

Elopara  . . 

St.  Lncia  Bay     . . 


Samarinda,  Koetei 

PHILIPPINE  ISLANDS. 
Palawan  .  • 


Manila,  Luzon    .  . 

CELEBES. 
Manado,  V  30'  N.,  124**  47'  E. 


Macassar. 


Island  of  Lombock 
Island  of  Timor.  • 


684 
666 
683 
461 
493 
1,037 

1,235 

1,210 

1,116 


911 

1,460  (about) 
1,804 

1,435 

969 

790 
1,361 


First  heard  on  26tli. 

First  beard  on  the  26tb. 

The  sounds  were  heard  on  the  27th. 

The  sounds  were  heard  on  the  26th  and  27th. 

First  heard  at  7  p.m.  26th;  loudest  at  11  a.m.  27th. 

The  sounds  appear  to  have  been  heard  only  on  the 
27th. 

See  also  the  note,  page  88,  by  Commander  Hon.  F. 
Vereker,  R.N.,  H.M.S.  Magpie. 

'*  It  seemed  as  if  heavy  guns  were  being  fired,  at  a 
distance  of  not  over  four  or  five  miles  away  *' 
(27th). 

"  The  noise  of  the  eruption  was  plainly  heard  all 
over  Borneo.  The  natives  inland,  who  murdered 
poor  Witti,  when  they  heard  the  noise,  thought 
we  were  coming  to  attack  them  from  the  east  and 
west  coasts,  and  bolted  away  from  their  village  " 
(26th-27th).  Letter  of  L.  von  Donop,  North 
Borneo. 

The  sounds  were  heard  on  the  26th  and  27th. 


**  The  detonations  were  heard  on  the  27th,  half-way 
up  the  Palawan  coast." 

The  sounds  were  imagined  to  be  signals  from  a  ship 
in  distress,  and  preparations  were  made  to  render 
assistance  (27th). 

The  sounds  are  said  to  have  been  heard  not  only  in 
the  town,  but  over  the  entire  province  in  which  it 
is  situated  (from  the  evening  of  the  26th  to  the 
27th). 

Two  steamers  were  sent  to  sea  on  the  27th  to 
ascertain  the  cause  of  the  reports.  The  sounds 
were  heard  over  the  whole  province. 

The  reports  were  heai*d  in  all  parts  of  the  island,  as 
well  as  in  the  adjoining  one  of  Bali  (26th-27th). 

The  sounds  were  heard  all  over  the  island.  A 
Government  steamer  was  despatched  to  ascertain 
their  cause  (26th-27th). 


84 


LIEUT-GENERAL  STRACHEY  ON  TBE  SOUNDS. 
Table  IX. — continu^^ 


Place. 


Distance  from 

Krakatoa, 

in  English  miles. 


Notes. 


NEW  GUINEA. 

Salwatty    Island,    North-west 
coast. 


Dorey,  Geelvink  Bay 


1,800 


2,014 


WEST 

AUSTRALIA 

Perth       . . 

.. 

Geraldton 

• .          •  • 

CoBsack  .. 

1,902 

1,675 
1,286 


Victoria  Plains  .. 


•1,700  (about) 


SOUTH  AUSTRALIA. 

Alice  Springs,  23**  41'  S.,  133° 

37' E. 

Undoolga,  25  miles  east  of  Alice 
Springs. 

Daly  Waters,  16^  18'  S.,  133^ 
25' E. 

Elsey  Creek,  15*  10'  S.,  133° 
23' E. 


2,233 

2,250  (about) 
2,023 
2,003 


*  The  Rajah  of  Salwatty,  whom  I  met  at  the  village 

of  Samatu,  told  me  that  the  noise  of  the  eruption 
had  been  audible  there.**  Dr.  F.  H.  Guillemard, 
M.A.,  F.L.S.     (No  date  given.) 

*  The  reports  were  heard  on  the  27th  by  M.  van 

Hasselt,  residing  at  Dorey,  and  recorded  at  the 
time  in  his  diary.  The  natives  reported  to  him 
that  they  had  heard  similar  sounds  on  the  26th. 
He  described  the  sounds  as  being  like  distant 
cannonading.**  Extract  from  letter  of  Dr.  F.  H. 
Guillemard,  M.A.,  F.L.S. 


"  This  coast  has  been  visited  (27th)  by  ...  .  sounds 
as  of  the  firing  of  guns  inland.'*  Staff-Commander 
Coghlan,  R.N. 

At  Geba^ldton  and  at  Cossack  the  meteorological 
observers  reported  that  sounds  were  heard  on  tha 
27th  resembling  heavy  guns,  the  reports  at 
Geraldton  being  preceded  by  a  rumbling  noise. 
The  observer  at  Cossack  says  that  similar  report<s 
were  heard  along  the  coast  from  the  Ash  burton 
to  the  Sherlock  rivers,  and  inland  as  far  as  the 
Hamhebsley  range. 

"  People  were  startled  by  hearing  a  series  of  loud 
reports,  resembling  those  of  artillery  at  a  distance 
in  a  north-westerly  direction.  The  first  sounds 
were  heai*d  by  a  few  persons  at  11  p.m.  on  Sunday 
(26th),  continuing  at  irregular  intervals  till 
about  4  p.m.  on  Monday ;  sometimes  as  many  as 
three  reports  occurred  in  a  minute,  but  generally 
there  was  a  few  minutes'  interval."  Western 
Australian,  September  4. 


•'  Two  distinct  reports,  similar  to  the  discharge  of  a 
rifle,  were  heard  on  the  morning  of  the  27th,  and 
similar  sounds  were  heard  at  a  sheep  camp  nine 
miles  west  of  the  station,  and  also  at  Undoolga, 
25  miles  east.'*     Report  by  Mr.  Skinner. 

"  On  Sunday,  the  26th,  at  midnight  we  were 
awakened  by  an  explosion  resembling  the  blasting 
of  a  rock,  which  lasted  for  a  few  minutes.  Next 
morning,  between  9.30  and  10  o'clock,  a  similar 
noise,  with  slight  vibration,  was  heard  and  felt,  oon- 
tinaing  for  15  minutes.  Men  camped  ^ve  miles 
south  of  Daly  Waters  also  heard  it,  and  the  noise 
was  heard  also  at  Elsey  Creek  and  other  places  on 
the  overland  telegraph."     Report  by  Mr.  Kemp. 


LIEUT.-GENERAL  STRACHEY  ON  THE   SOUNDS. 


85 


Table  IX. — continued. 


Place. 


BURMA  H. 


Mergui 
Tavoy 


BiBtAnoe  from 

Krakatoa, 

in  English  miles. 


Notes. 


NICOBAB   ISLANDS. 

ANDAMAN   ISLANDS. 
Port  Blair 


CEYLON. 


1,366 
1,478 


1,299 


1,500 


Dutch  Bay 


Hambantota       . , 

Tissa  Mab&  lUma  (near  Ham- 
bantota). 


North  Namona  Koolie,  Badalla, 


Tumpalancholai      and      Mabd 
Oja  (on  the  Badalla  road). 


2,058 

1,866 
1,870  (abont) 

1,904 
1,893 


The  sounds  were  heard  on  the  26th  and  27th. 

**  All  day  on  August  the  27th  unusual  sounds  were 
heard,  resembling  the  boom  of  guns.  Thinking 
there  might  be  a  wreck  or  a  ship  in  distress,  the 
Tavoy  Superintendent  sent  out  the  police  launch, 
but  they  could  see  nothing." 


'*  Extraordinary  sounds  were  heard,  as  of  guns 
firing"  (26th-27th),  Extract  from  report  by 
officer  in  charge. 


*'  At  9.30  p,m.  on  the  26th  a  report  was  heard  as  of  a 
distant  signal  gun.  Steamer  was  sent  round  the 
coast  to  search  for  the  vessel  supposed  to  be 
firing  as  signals  of  distress.  Similar  sounds 
were  heard  at  irregular  intervals  during  the  two 
following  days."  Extract  from  letter  of  Mr.  E. 
g.  Man. 

**  Several  reports  were  heard  in  Port  Blair,  sup- 
posed to  be  from  some  ship  in  distress.  Weather 
between  August  the  27th  and  29th  very  unsettled, 
and  heavy  rain  and  wind  prevailed."  Extract 
from  Port  Offiper's  report, 


The  sounds  were  heard  from  7  a.m.  to  10  a.m.,  27th. 

"  Reports  heard  by  three  persons  from  7  a,m.  on  the 
26th,  and  by  many  persons  during  the  26th,  on  the 
night  of  the  26th'27th,  and  during  the  27th. 
The  usual  style  was  a  steady  sequence  of  reports, 
and  then  a  rapid  saccession  of  them,  ending,  very 
often,  in  a  loud  bu?«t  of  two  or  three,  or  half  a 
dozen,  almost  together,  which  was  generally  fol- 
lowed by  a  lull.  The  intensity  of  the  sounds 
varied  greatly." — Letter  from  Mr.  H.  Parker. 

Heard  at  noon  on  the  27th,  and  continued  for  half 
an  hour,  **  I  thought  it  might  be  some  volcano 
in  action  out  at  sea,  or  else  ships  firing  heavy  guns." 

**  Captain  Walker  and  Mr.  Fielder  were  puzzled  at 
various  times  during  the  forenoon  of  the  27th, 
by  hearing  noises  as  if  blasting  was  going  on, 
though  there  was  nothing  of  the  sort  for  a  very 
considerable  distance,  if  anywhere  in  the  district." 


N 


86 


LIEUT.-GBNERAL   STRACHEY  ON  THE   SOUNDS. 
Table  IX. — continued. 


Place. 


Distance  from 

Krakatoa, 
in  English  miles. 


Notes. 


Mullijavalai 


1,996 


Bambodde 
Madulsima 

Batticaloa 


1,888 
1,902 

1,888 


Kalmnnai 


1,877 


Kokkulai 
Chemmalai 
Kotinalie  Valley 

Bogawanialawa . 

Galle        .. 
Mann&r   .. 


1,980 
1,980 
1,928 

1,911 

1,932 

2,047 


} 


''  The  District  Mudalijar  reported  that  sonnds  were 
heard,  as  if  cannon  were  being  fired,  from 
midnight,  Aagost  26th,  till  noon,  Augnst  27th. 
The  sounds  seemed  to  come  from  the  east,  and 
from  no  g^reat  distance.  The  apparent  proximity 
of  the  explosions  reported  from  the  Mnlliyayalai 
Patta  may  have  been  due  to  the  hilly  nature  of 
the  country  there.*'  Report  by  Mr.  S.  Haughton, 
Assistant  Qoyemment  Agent. 

Sonnds,  resembling  distant  guns,  were  heard« 

At  first  the  sounds  were  thought  to  be  those  of 
guns  fired  at  Trincomalee.  First  heard  on  the 
26th. 

^' At  about  midnight,  2Gth,  I  heard  about  five  or  six 
times  a  noise  as  of  a  cannon,  at  intervals  of  15 
minutes,  towards  the  east.  On  the  morning  of 
the  27th,  too,  about  three  times  I  noticed  a  noise 
similar  to  that  of  the  discharge  of  a  cannon  over 
the  sea  towards  the  east."  From  Signaller's 
report.  ^'  The  Sub-Collector  states  that  at  about 
6  p.m.  on  the  evening  of  the  26th  he  heard  a  loud 
report,  as  if  a  cannon  was  discharged  down 
southward,  which  he  and  the  people  near  him 
thought  to  be  thunder.*'  Report  by  Mr.  Elliott, 
Acting  Governn^ent  Agent. 

''Mr.  Christie,  of  the  Public  Works  Department, 
told  me  he  had  heard  loud  explosions  seawards 
that  morning  (27th),  and  that,  as  they  seemed 
like  the  discharge  of  heavy  artillery,  he  presumed 
some  man-of-war  was  practising  with  her  big 
guns  out  of  sight  of  land,  as  he  could  see  no 
ships."     Report  by  Mr.  Elliott. 


Sounds  as  of  firing  of  cannon  at  Trincomalee. 


The  sounds  were  heard  on  the  27  th. 

''  The  sounds  were  heard  here  most  distinctly.  They 
were  like  blasting  on  the  BillhuUoya  side,  and 
kept  on  all  day,  from  7.30  a.m.  till  4p.m."  (27th). 

The  sounds  were  heard  on  the  27th. 

"Loud  sounds,  resembling  the  report  of  distant 
cannon,  were  heard  to  the  eastward  on  the  27th." 
Report  by  Mr.  Fowler,  Assistant  Government 
Agent. 


LIEUT.-GENERAL  STRACHEY  ON  THE  SOUNDS. 


87 


Table  IX. — continued. 


Place. 


Distance  from 

Krakatoa, 

in  English  miles. 


Notes, 


Xotaimunai 


Lunngala 


1,900  (about) 


i; 


CHAGOS  ISLANDS. 
Diego  Chu'cia 


2,267 


BODBIGUEZ. 


2,968 


VESSELS  AT    SEA. 

Barque     Wm,    H.    Besse— Oft 
Northern  portion  of  Java. 


Ship  Charles  Bal 


Ship  Barjild 


SS.  Anerley — ^Prom  the  Strait 
of  Banca  to  near  the  North 
Watcher  Island. 

Ship  (?  name)  —  Off  Lepa 
Island. 


From  about  40  to 
20ea8tofE:raka- 
toa.  Vessel  ap* 
preaching  the 
volcano. 

From  aboat  11 
south  to  67  N.E. 
of  Krakatoa. 

About  75  east  of 
Krakatoa. 

From  about  250 

to  90  N.E.  of 

E^rakatoa. 

About  230  N.N.E. 
of  Krakatoa. 


"  I  heard  distinctly,  at  about  6  p.m.  on  the  26th 
(local  time),  a  loud  report,  as  if  a  cannon  was 
discharged  down  southward."  Report  bj  Mr. 
Alfred  Koch. 

Like  heavy  guns  fired  at  sea  in  the  direction  of 
Hambantota  on  the  27th. 


"  Le  lundi  27  Aoiit  entre  10  et  1 1  heures  du  matin, 
pendant  le  dejeuner,  nous  avons  entendu  des 
detonations  sourdes  mais  violentes.  Nous  avons 
cru  tellement  k  Tappel  d*un  navire  en  d^tresse 
oue  nous  avons  couru  et  que  j'ai  envoye  plusieurs 
homnies  ve1*s  le  rivage  exterieur  de  Tile  sur 
plusieurs  points  diff^rentes,  en  observation.  Le 
Capitaine  Florentin,  de  VEva  Joshua,  et  son 
second  M.  Daniel  Sauvage,  venaient  de  quitter 
Pointe  de  Test  pour  aller  mouiller  k  Pointe 
Marianne,  lorsqu'ils  ont  entendu  les  m^mes 
d^touations.  lis  ont  aussitot  envoy^  des  hommes 
en  observation  k  reztremit^  des  mAts.  Mais 
comme  les  miens  ils  n'ont  rien  vu."  Extract  from 
letter  of  M.  Lecomte. 


^*  Several  times  during  the  night  of  the  26th~27th 
reports  were  heard  coming  from  the  eastward, 
like  the  distant  roars  of  heavy  guns.  These  re- 
ports continued  at  intervals  of  between  three  and 
four  hours,  until  3  p.m.  on  the  27th  (=  5*48  p.m. 
local  time  at  Krakatoa),  and  the  last  two  were 
heard  in  the  direction  of  Oyster  Bay  and  Port 
Mathurie."  Report  by  Mr.  James  Wallis,  Chief 
of  Police. 

"  Throughout  the  afternoon  and  night  of  the  26th 
we  heard  heavy  reports,  like  the  discharge  of 
heavy  artillery.  At  10  a.m.  on  the  27th  we  heard 
some  terrific  reports." 


"The  sounds  were  very  intense,  and  continuous 
from  3.30  p.m.,  26th,  to  1.30  p.m.,  27th. 


At  anchor  near  Great  Kombuis  Island  throughout 
the  27th. 

"  Noise  on  the  27th  resembled  distant  cannonading." 
"  The  detonations  were  heard  all  over  the  Ishmd 
of  Banca  during  the  26th-27th." 

The  sounds  were  first  heard  on  the  26th. 


N  2 


88 


LIEUT-GENERAL  STBACHEY  ON  THE  SOUNDS. 


Table  IX. — contintied. 


Place. 

Distance  from 

Krskatoa, 
in  Engliflh  miles. 

Notes. 

Brig  Airlie  —  LsLt  0**  30'  S., 
Lon.  lOS''  54'  E. 

390 

**At  3  p.m.  26th.     Sonndfl    like  those  of  heavy 
artillery,  which  continued    till    about    10    p.m. 
The  last  report  made  the  ship  tremble  all  over." 

Ship  Ida— Lat.  2''  42'  K,  Lon. 
108°  12'  E. 

622 

The  sounds  were  heard  on  the  27th  to  the  south* 
south-eastward. 

H.M.S.  Magpie— Ls^t.y  52' N., 
Lon.  118^22'  E. 

1,227 

"The  noise  of  the  detonations  caused  by  Mount 
EIrakatoa,  resembling  distant  heavy  cannonading, 
was  distinctly  heard  by  us,  and  by  the  inhabitants 
of  this  coast  as  far  as  Banguey  Island,  on  August 
27th."    Conunander  Hon.  Foley  C.   P.   Vereker, 
R.N. 

Barque    Charlotte— Trom  Lat. 
11"  42'  S.  and  Lon.  107°  54' 
B.,  to  Lat.  8*  18'  S.  and  Lon. 
106°  42' E. 

414  to  166  • 

The  sounds  of  the  explosions  were  heard  from  5  p.m. 
26th  tiU  10  a.m.  27th. 

Brigantine    Adriatio — ^Lat.  10** 
S.,  Lon.  106°  E. 

265 

The  sounds  of  the  explosions  were  heard  on  the 
26th  and  27th. 

Barque  Jbnc—Lat.  4"   46'    S., 
Lon.  90°  E.,  to  Lat.  7"  45'  S., 
Lon.  93°  E. 

1,072  to  865 

Sounds  were  heard  on  the  26th  and  27th. 

Brig  Catherine— Ls,t  6°  31'  S., 
Lon.  86°  46'  E.,  to  Lat.  9**  S., 
Lon.  87°  19'  E. 

1,291  to  1,268 

The  sounds  were  first  heard  on  the  evening  of  the 
26th. 

Brig    Pmm— Lat.    1°    39'    S., 
Lon.  92' 17' E,  to  Lat.  2°  59' 
S.,  Lon.  92°  11'  E. 

944  (mean) 

"  Constant  peals  of  thunder  were  heard  on  the  26th 
and  27th  in  the  direction  of  Sumatra,  but  with- 
out any  appearance  of  lightning." 

Ship  Lennox  Ocwrf/e— Lat.  0°  0', 
Lon.  91°  23'  E. 

1,060 

The  sounds  were  heard  on  the  26th. 

Ship  Barfcarowo— Lat.  1°  42'  S., 
Lon.93M2'E.,to  Lat.  2'*  36' 
S.,  Lon.  92°  54'  E. 

900 

Sounds  heard  on  the  27th  in  south-east  like  gnns  or 
distant  thunder,  but  no  lightning  visible. 

Kjvkatoa,  Rep  Hoy.  Soc.  Con\, 


Flate   W. 


ENIJ^GED  COPIES  OF  BAR0(3lAMSpR(MnGHTSEIJ;CT^    STATIONS 
SHOWING  THE  CHARACTER  of  the  first  TOUR  OSCILLATIONS. 


ist 


2^ 


3^ 


Wiashuiffton. 


Toronto. 


Aberdeen, 


BomJbay, 


Zi-KcL-Wet, 


Copies  of  the  record,  of 
-were  received  fbr  the 


another  instrument 
^and4^osci2latu)ns. 


Mauritius. 


Melboume. 


South.  Georgia, 


Majby  &  SoTUi,  l.irh  . 


Z^a]caZoa,.B^.B^y.SocCom.  BAROMETER     CURVES 

AUGT  &  SEPT^_1883. 


Plate  Vm 


-H 


H- 


-■)    + 


\.  ^-  ^_ 


V    ! 


-f  - 


I      I 


.3 


v- 


--H 


--H 


-  -i 
I 

-  I 


TiriiLiiiiUTiL: 


^1 


rr- 


n  ■  H 


-H 


irTtrntTii 


tnilTiJ 


iimu 


30^ 

IIOOW 

TTTPTT 


w 


in 


tr^-^ 


^ 


j:::Li:ijnliim:it 


1 1 1 1 1 J 


1»* 

MIOT     HOOK 


i-^.... 


:<n; 


.  1. 
I 


tCT  IHXELTt: 


m 


UTTirr 


Wiidhin^rtan, 


Nen  IbrJc 


Thn*rtto 


\Iiston 


Cohnbra 


SanRmandi* 


ThUncu'> 


\jSun\ouAi 


.Jrr.UMff): 


ffla^ffaif 


Iw^i^T>Oi>l 


'hurat 


un 


Orept^yyi 


^Mo/ife    I 


\BiukLPe^ 


lodtidaK 


S^Mavhurg 


Jloavlom?k 


KaiTtbda 


Bofihc^ 


Ccd'Adti 


Zi-l  w-H  et 


MeSfOUTie 


^Sydney 


Tohko 


WelUn^n 


S^Oeat>ffia 


JheMark  \  indicator  Iht  part  of  the  tnart  seiectod  for  Measta-ement. 


caca.Rep.  Roy.  Soc.  Com.. 


Plate  IX. 


RETDTJCED   COPY  OF  A  PORTION  OF  THE 
RECORD   OF  PRESSURE  ON  THE 

BATAVIA    GASOMETER 

27"?^  AUGUST,    1883. 


-  lEowr. 


^lOmnu    \Oriffirua.  ScaUs. 


Malb/  &  Sons.Lith. 

Stt  note,  in  text  p.  73. 


The  Scale  onihe  originxxL drngrairvteTnanja^  aJbthe point  mxxrked.  mtJh  cv dotted Une. 


sr.m  Rep.  Roy.  Soc.  Com,. 


FhxieX. 


WAVEN?I. 

FIRST     PASSAGE    FROM 

KRAKATOA 

TO  THE 

ANTIPODES 


WAVE  N?  II 


IL 


FIRST     PASSAGE    FROM 

ANTIPODES 

BACK  TO 

KRAKATOA 


m 


Maib^'-  <fc  Sons,  Lttm 


X  Eep  Roy.  Soc.  Corrt 


WAVE  ]S°  ni . 


Plate  JU. 


SECOND     PASSAGE    FROM 

KRAEATOA 

TO  THE 

ANTIPODES 


WAVE  N«IV, 


SECOND     PASSAGE    FROM 

ANTIPODES 

BACK   TO 

KRAKATOA 


MaJtry  *  Sons,  Jjth 


^ccoion,R.ep.  Roy.  Soc.  Com. 


Fixite  xn. 


WAVE  N^  V. 


THIRD     PASSAGE    FROM 

KRAEATOA 

TO  THE 

ANTIPODES 


WAVE  N°  VI . 


THIRD     PASSAGE    FROM 

ANTIPODES 

BACK   TO 

KRAKATOA 


Mailry  &  Sonr.,  lafh 


liatoa.  Rep.  Roy.  Soc.  Com,. 


Flatem. 


vm 


WAVEN?Vn. 

FOURTH     PASSAGE    FROM 

KRAKATOA 

TO  THE 

ANTIPODES 


122 


/lie 


1                          ^^ 

-^^x* 

«'^ 

--^^ 

1                          ^ 

c:--^___^ 

120 

X  i**,^- 

\                      J/\ 

■/^ 

^^^^ 

j\f  Ic 

\                                                y^/ 

"iX 

/  ^ 

---^^^^ 

/  W  ^-'-"'r^ 

\                           j/y^ 

/  \   r^ 

^""^^ 

/       vC'^^^  s 

\                  yy'^ jt 

/     \J 

1 

\\. 

\   yy/ 

/ 

V 

\y'  j^ 

/ 

\ 

^^^^ 

'     \ 

\y 

^ 

^&^ 


o" 


Mallry  &  Soils.  JAxl^ 


KfixJcaZoa,.  Rep.  jj 


PlateJOV. 


THE    EARTH'S    R0TATI0:N^. 


f 


I 


European 


j- American 

^ Australian 

\ Tropics 


CENTRAL 
LINE 


Maloy  ^  Sons,  JitK. 


PlaU^  M 


J 


ilaiixy  £c  Sons,  -Lith 


KraJcatocu,  R&p  Roy.  Soc.  Com.. 


Flate,m. 


MAP   SHOWING  THE  PLACES  AT  WHICH  THE   SOUNDS 

OF    THE  ZXPLOSIOTJS  ■WERE   HEARD    ON   AUGUST  26-27 
THE     SHADED    PORTION    INDICATES    APPROXIMATELY     THE  AREA    OVER   WHICH    THE  SOUNDS   WERE   HEARD. 


PART  ni. 


ON   THE   SEISMIC   SEA  WAVES   CAUSED  BY  THE  ERUPTION  OF 
KRAKATOA,  AUGUST  26TH  AND  27th,  1883. 

By  Captain  W.  J.  L.  Whabton,  E.N.^  F.R.S.,  in  completion  of  the  unfinished  Notes 
of  Captain  Sir  F.  J.  Evans,  RN.,  KC.B.,  F.E.S. 

[In  this  Part  Oeographical  miles  alone  are  naed.] 


On  the  lamented  death  of  Sir  Frederick  Evans,  an  examination  of  the  papers 
connected  with  the  sea  disturbance  consequent  upon  the  eruption  of  Krakatoa, 
on  which  he  was  at  work,  revealed  a  number  of  notes  showing  that  he  had  made 
considerable  advance  with  their  discussion.  I  was  requested  to  look  at  these 
unfinished  notes  ;  and  at  first  I  came  to  the  conclusion  that  a  small  amount  of  labour 
would  suffice  to  complete  them.  When,  however,  I  took  upon  myself  to  do  this,  I  soon 
found  that  I  had  miscalculated  the  task,  and  that  the  notes  left,  though  very  clear, 
were  but  the  preliminary  foundation  of  the  report ;  and,  moreover,  that  it  would  be 
impossible  to  carry  it  on  where  Sir  F.  Evans  had  left  off,  as  many  points  presented 
themselves  which  required  a  thorough  examination  of  the  mass  of  original  matter. 

Sir  F.  Evans  had  commenced  to  form  a  table  of  the  speed  of  the  waves,  and  his 
notes  related  principally  to  the  selection  of  the  crests  marked  on  the  different 
diagrams  as  those  identical  with  the  first  arrival  of  the  great  wave  from  Krajtatoa. 
These  I  have  verified,  and  in  nearly  every  case  have  come  to  the  same  conclusion  as 
Sir  F.  Evans. 

For  the  text  of  the  report  and  the  deductions  which  I  have  made  I  alone  am 
responsible,  as  no  cliie  was  left  as  to  any  opinion  Sir  F.  Evans  may  have  formed 
on  the  different  points  raised. 

The  time  used  throughout  is  civil  mean  time  in  days  of  24  hours,  counting  fi-om 
midnight.  In  the  text,  local  time  is  referred  to.  For  the  calculation  of  the  periods 
of  translation  of  the  waves,  the  time  is  reduced  to  Greenwich  civil  time,  but  this  is 
given  only  in  the  tables  showing  the  net  results  of  the  investigation. 


90  CAPTAIN   WHARTON   ON   THE   SEISMIC    SEA   WAVES. 

Accouvt  of  the  Phenomena  relating  io  Sea  Disturbance  in  the  immediate  vicinity  of 

Krakatoa. 

Mr.  R.  D.  M.  Verbeek,  a  Dutch  mining  engineer  resident  at  Buitenzorg,  a 
town  situated  in  the  interior  of  Java,  about  30  miles  south  of  Batavia,  has  collected 
all  the  evidence  forthcoming  of  the  details  of  the  eruption  of  Krakatoa  which  com- 
menced on  May  the  20th,  1883,  and  culminated  on  August  the  27th.  This  he  has 
published  in  his  work  "  Krakatau"  Parts  I.  and  II.,  which,  accompanied  by  charts 
and  sketches,  forms  a  complete  history  of  the  outbreak  and  its  effects  in  the 
immediate  vicinity. 

As  this  is  accessible,  a  comparatively  brief  statement  of  the  leading  proven 
or  accepted  facts  in  connection  with  the  great  sea  disturbance  in  the  immediate 
neighbourhood  of  the  eruption  will  probably  suffice  as  an  introduction  to  the  con- 
sideration of  the  question  of  its  propagation  to  distant  shores.     {See  also  Part  I.) 

During  the  earlier  eruption  in  May,  and  up  to  August,  no  remarkable  movement 
of  the  water  was  observed.  The  violence  of  the  explosions  recommenced  diuring  the 
early  afternoon  of  the  26th  of  August,  a  particularly  heavy  detonation  being  heard 
at  about  17.30  on  that  day. 

This  was  marked  by  the  pressure  gauge  of  the  gas  works  at  Batavia  at  about 
the  same  time;  and,  between  18  and  19  hours,  the  first  large  wave  reached 
the  Java  shore  at  Tyringin,  24  miles  from  Krakatoa,  where  it  destroyed  many 
houses  near  the  sea.  At  about  the  same  time  a  wave  caused  considerable  damage 
at  Telok  Betong,  at  the  head  of  Lampong  Bay  in  Sumatra,  44  English  miles  from 
Krakatoa. 

At  about  19  hrs.,  or  19  hrs.  30  mins.,  the  low-lying  Chinese  Camp  at  Merak  was 
swept  away.     At  Anjer  this  wave  was  only  about  5  feet  high. 

From  this  time  the  sea  in  the  Strait  of  Sunda  was  much  agitated,  but  no  further 
large  wave  is  recorded  until  the  morning  of  the  27th. 

On  the  27th  at  1  hr.  the  village  of  Sirik,  6  miles  south  of  Anjer,  was 
submerged ;  and  one  account  mentioas  a  wave  at  Telok  Betong  at  1  hr.  30  mins. 

At  about  6  hrs.  30  mins.  a  wave  swept  away  nearly  the  whole  of  Anjer,  which 
lay  low,  and  this  was  followed  at  about  7  hrs.  30  mins.  by  another,  which  completed 
the  destruction.  At  the  same  time  the  lower  part  of  Telok  Betong,  in  Sumatra,  was 
overwhelmed.  Two  heavy  air  waves  are  recorded  on  the  gas  pressure  gauge  at 
Batavia  at  5  hrs.  43  mins.  and  6  hrs.  57  mins.,  which  are  probably  connected  with 
the  explosions  causing  these  waves. 

At  some  time  a^ter  10  o'clock  an  immense  wave  inundated  the  whole  of  the 
foreshores  of  Java  and  Sumatra,  bordering  the  Strait  of  Sunda,  and  carried  away 
the  remaining  portions  of  the  towns  of  Tjrringin,  Merak,  and  Telok  Betong,  as  well 
as  many  other  hamlets  and  villages  near  the  shore. 


CAPTAIN   WHARTON   ON  THE   SEISMIC   SEA  WAVES.  91 

To  this  wave,  undoubtedly  the  largest,  must  be  attributed  the  disturbance  which 
spread  so  far  over  the  surface  of  the  ocean. 

At  places  comparatively  near  and  immediately  exposed  to  the  direct  disturbance 
emanating  from  Krakatoa,  no  mention  is  made  of  waves  after  this  great  one,  nor  is 
even  the  great  wave  itself  recorded.  The  darkness,  and  the  fact  of  all  the  survivors 
of  the  6  hrs.  30  mins.  and  7  hrs.  30  mins.  waves  having  fled  from  the  shore,  are 
sufficient  to  axscount  for  this  omission.  At  the  lighthouse  at  Vlakke  Hoek  alone,  the 
great  wave  is  said  to  have  repeated  itself  three  times  at  intervals  of  about  half-an- 
hour. 

At  one  or  two  places  outside  the  Strait  the  waves  were  observed  to  continue. 
Thus  at  Tjabang,  about  90  miles  to  the  north,  in  Sumatra,  eleven  waves  were  counted 
between  15  hours  on  the  27th  and  6  hours  on  the  28th.  At  Batavia,  the  disturbance 
lasted  from  noon  on  the  27th  to  midnight  on  the  28th  ;  and  fourteen  waves,  with  a 
steady  period,  were  marked  on  the  tide  gauge.  As  the  explosions  of  the  volcano 
•continued  during  the  whole  of  the  27thj  it  may  fairly  be  assumed  that  some  other 
waves  were  generated  subsequent  to  the  10  o'clock  one. 

After  16  hrs.  ao  mins.  the  detonations  are  mentioned  as  gradually  diminishing  in 
force  until  6  hours  on  the  28th. 

Several  ships  were  in  the  Strait  during  the  great  eruption  and  experienced 
terrible  weather,  heavy  squalls  from  different  directions,  confused  sea,  lightning,  and 
a  rain  of  mud,  ashes,  and  pumice.  None  of  these  ships  mention  any  particularly 
large  waves,  nor  was  any  damage  done  by  the  sea.  One  vessel  at  anchor  six  miles 
from  St.  Nicholas  Point,  mentioned  a  rapid  current  of  10  knots  an  hour  (estimated) 
running  towards  the  volcano  some  time  after  the  great  explosion* 

It  is  specially  worthy  of  remark  that  no  earthquake  shock  is  recorded  at  any 
time  during  the  eruption,  except  on  the  evening  of  the  26th,  when,  at  Anjer,  the 
earth  is  said  to  have  trembled. 

When  the  site  of  the  eruption  could  be  examined^  it  appeared  that  the  following 
changes  had  taken  place : — 

Of  the  north  part  of  the  island  of  Krakatoa,  an  area  of  nearly  six  miles,  with 
an  average  height  of  7oO  feet,  had  disappeared,  on  which  the  sea  rolled  of  a  depth 
not  yet  ascertained,  but  over  150  fathoms  in  some  places.  Taking  the  average  height 
of  the  missing  portion  to  be  700  feet,  and  the  present  depth  at  300  feet,  the  mass  of 
matter  thus  blown  away  may  be  considered  as  1^  cubic  miles. 

The  portion  of  the  island  that  remained  seems  to  have  received,  according  to 
Mr.  YfiEBEEK,  an  addition  of  about  'one  square  mQe,  by  upheaval  on  the  side  remote 
from  the  portion  which  disappeared.  This  cannot  be  considered  very  certain,  seeing 
that  the  former  sm^vey  by  Mr.  J.  Richards,  R.N.,  did  not  pretend  to  be  accurate,  as 
the  original  in  the  Hydrographic  Department  shows. 

The  Peak,  2,647  feet  high  (Richards's  Survey),  had  been  shorn  in  two,  leaving  on 
the  north  face  of  the  remaining  portion  a  precipitous  cliff  of  the  same  height 


92  CAPTAIN   WHARTON   ON   THE   SEISMIC   SEA  WAVES. 

Verlaten  Island,  which  lay  close  to  the  north-west  of  Krakatoa,  had  a  super- 
ficies of  about  one  square  mile  before  the  eruption.  It  now  has  an  area  of  nearly 
three  miles. 

Lang  Island,  to  the  north-east,  and  also  close  to  Krakatoa,  was  little  changed,  but 
had  received  a  slight  addition  on  its  northern  side. 

Two  smaU  new  islands  of  mud  and  pumice,  almost  a-wash,  standing  on  extensive 
banks,  had  made  their  appearance  seven  miles  to  the  northward  of  Krakatoa,  where 
formerly  a  depth  of  80  feet  existed. 

The  depths  over  an  area  of  140  square  miles  around  Krakatoa  had  undergone 
alterations;  in  most  cases  upheaval  having  taken  place,  but  in  some,  subsidence.  The 
precise  amount  is  difficult  to  estimate,  as  the  old  sounduigs  were  in  many  parts 
scanty,  but  the  general  fact  of  change  may  be  taken  for  granted, 

Eeyond  this  area,  no  alteration  has  yet  been  discovered  in  the  depth  of  the  sea, 
so  that  the  movement  is  assumed  to  have  been  comparatively  local.  The  first  reports, 
to  the  effect  that  the  whole  of  the  Strait  of  Sunda  had  been  altered,  were  exaggera- 
tions. 

In  one  part  the  change  is  very  marked,  and  materials  exist  for  more  detailed 
statements.  Between  Lang  Island  and  Sebesi,  over  an  area  of  about  72  square 
miles,  the  depths  are  greatly  reduced.  The  bank,  18  mile^  ia  area,  on  which  the  two 
new  islands.  Steers  and  Calmeyer,  stood,  has  now  an  average  depth  of  12  feet,  where 
formerly  it  had  120  feet.  Over  the  remainder  of  this  area,  or  p,bout  59  square  miles, 
the  reduction  in  depth  averages  about  30  feet.  The  Chart^^  Nos,  1  md  2,  show  the 
condition  of  the  Strait  before  and  after  the  eruptiou. 

The  times  of  arrival  of  the  waves  at  different  plitces  on  the  shores  of  the  Strait 
are  but  vaguely  noted,  and  this  is  especially  the  case  with  the  great  wave  after 
10  o'clock  of  the  27tb.  Terror  and  dismay  reigned  everywhere,  and  darkness  had 
settled  over  the  land.  At  Anjer,  also,  where  this  wave  must  have  come,  no  one  was 
left  to  see  it,  the  few  survivors  having  fled  to  the  hills. 

To  some  extent  the  same  uncertainty  attaches  to  the  height  of  the  waves. 
All  who  observed  the  wave  after  10  o'clock,  however,  agree  that  it  was  the  largest, 
and  this  is  supported  by  all  the  evidence  forthcoming.  As  this  wave  alone  appears 
to  have  travelled  to  places  at  great  distances,  it  is  the  most  important.  All  observa- 
tions founded  on  measurements  of  the  marks  left  by  the  water  are  considered  as 
relating  to  this  wave. 

The  inundated  portions  of  the  shores  of  the  Strait  of  Sunda  are  indicated  on 
map,  p.  17,  and  Mr.  Yerbeek  also  mentions,  in  his  account  of  the  disaster;  the 
maximum  height  in  different  localities.  It  is  not,  however,  stated  by  whom  the 
contours  on  Mr.  Verbeek's  maps  were  obtained,  nor  is  the  means  of  obtaining  the 
limit  reached  by  the  water  stated  in  every  case.  As  far  as  can  be  gathered,  the 
following  were  the  altitudes  to  which  the  wave  attained  at  places  on  each  shore  of 
the  Strait  of  Sunda,  and  in  the  immediate  vicinity  of  the  volcano. 


CAPTAIN   WHARTON   ON  THE   SEISMIC   SEA   WAVES.  93 

Java  Shore. 

At  Merak,  33  miles  from  Krakatoa,  the  height  of  the  wave  was  estimated  by 
Mr.  McCoLL  to  be  135  feet ;  by  Mr.  Nieuwenhuys,  an  engineer,  100  feet.  It  does 
not  appear  on  what  these  estimates  are  based.  The  greatest  height  measured  at  which 
buildings  were  washed  away  was  47  feet.  Mr.  Verbeek,  on  his  plan,  shows  the  hill 
sides  to  have  been  washed  by  the  water  to  a  height  of  115  feet.  The  peculiar 
position  of  Merak,  standing  at  the  head  of  a  funnel-shaped  strait  formed  by  the 
island  of  Merak,  may  have  caused  the  wave  to  be  higher  there  than  elsewhere. 

At  Anjer,  26  miles  from  Krakatoa,  the  height  of  the  wave  at  6  hrs.  30  mins.  is 
stated  to  have  been  over  33  feet.    The  subsequent  and  higher  waves  are  not  appraised. 

At  Tyringin,  24  miles  from  the  volcano,  50  feet  is  mentioned  as  the  measured 
height  of  the  water  at  one  spot.  As  people  who  gained  the  hills  at  the  back  of  the 
plain,  stated  to  be  67  to  100  feet  high,  were  saved,  it  does  not  appear  that  the  wave 
could  have  been  much  over  70  feet. 

At  Princes  Island,  25  miles  distant,  the  water  is  said  to  have  attained  a  height 
of  50  feet. 

Surtiaira  Shore. 

At  Katimbang,  19  miles  from  Krakatoa,  the  wave  is  stated  by  Mr.  Verbeek  to 
have  reached  a  mean  height  of  80  feet. 

At  Telok  Betong,  the  water  reached  within  6  feet  of  the  top  of  the  hill  on  which 
the  Residence  stands  at  a  height  of  78  feet,  and  was  consequently  72  feet  high.  This 
seems  the  most  accurate  measurement  of  aU  those  given.  The  man-of-war,  "  Berouw^^ 
was  carried  1  '8  miles  inland  up  the  valley,  and  left  about  30  feet  above  the  level  of 
the  sea. 

At  the  lighthouse  on  Vlakke  Hoek  the  water  rose  50  feet. 

From  these  different  measurements  I  have  assumed  that  the  actual  height  of 
the  wave,  before  it  reached  the  shore,  was  about  50  feet. 

To  ascertain  the  time  of  the  genesis  of  the  great  wave  is  not,  at  first  sight,  easy, 
nor  can  it  by  any  means  be  arrived  at  with  certainty. 

How  the  wave  was  formed,  whether  by  large  pieces  of  the  mass  of  the  island 
falling  into  the  sea ;  by  a  sudden  submarine  explosion ;  by  the  violent  movement  of 
the  crust  of  the  earth  under  the  water ;  or  by  the  sudden  rush  of  water  into  the 
cavity  of  the  volcano  when  the  side  was  blown  out — ^must  ever  remain,  to  a  great 
extent,  uncertain;  but  more  of  this  hereafter.  What  precisely  took  place  during  this 
tremendous  outburst  no  one  knows.  The  island  was  shrouded  in  smoke  and  fire,  and 
was  never  clearly  seen  ;  nor  did  any  vessel  approach  near  enough  to  note  any  changes 
in  its  outline  during  the  eruption.  It  is,  however,  evident  that  the  three  larger  waves 
were  intimately  connected  with  the  three  great  explosions,  for,  though  the  testimony 

o 


94  CAPTAIN    WHARTON   ON   THE   SEISMIC   SEA  WAVES. 

of  ear-witnesses  is  not  clear  on  the  point  of  the  comparative  force  of  the  different 
detonations,  as  measured  by  the  sound,  happily  the  pressure  gauge  at  the  gasworks  at 
Batavia,  before  mentioned,  gives  no  uncertain  evidence. 

This  has  already  been  referred  to  also  in  Part  II.,  p.  69,  and  the  record  is 
reproduced  in  Plate  IX.,  whence  it  will  be  seen  that  the  three  largest  movements. 
Viz.,  those  at  5  hrs.  4^  mins.,  6  hrs.  57  mins.,  and  10  hrs.  18  mins.,  were  all  apparently 
connected  with  the  highest  three  waves  recorded.  As  far  as  that  at  10  hrs.  18  mins. 
is  concerned,  there  is  reason  to  believe  that  the  sea  and  air  waves  were  formed 
practically  synchronously. 

Batavia  is  distant  83  miles  in  a  straight  line  from  Krakatoa.     Thus,  deducting 
8  minutes  for  the  time  taken  by  the  air  wave  to  travel  this  distance,  and  5^  minutes 
for  the  difference  of  longitude,  the  time  of  genesis  of  the  air  wave  would  be  10  hrs 
4^  mins.  of  Krakatoa  time.* 

The  tide  gauge  at  Batavia  also  affords  valuable  evidence  and  an  independent 
means  of  arriving  at  a  time  for  the  starting  of  the  great  wave.  This  automatic 
instrument  has  recorded  the  idrst  great  wave  at  36  minutes  past  noon.  The  time 
taken,  according  to  the  formula,  V=\/^,  by  a  wave  in  travelling  the  distance 
between  the  two  places  (100  sea  miles),  and  in  the  depths  shown  by  the  excellent 
chart  which  exists,  is  2  hrs.  80  mins.  Deducting  this  and  the  5^  minutes'  difference 
of  longitude,  we  get  10  hrs.  0  min.,  Krakatoa  time,  as  the  hour  at  which  the  great 
wave  left  the  island.  This  I  have  adopted,  and  I  find  that  Mr.  Verbeek  has  come 
to  the  same  conclusion. 

On  account  of  the  intricacy  of  the  route,  this  result  can  be  considered  approxi* 
mate  only,  but  the  agreement  with  the  other  determination  is  sufficiently  near  to 
corroborate  the  substantial  accuracy  of  tlie  time  assumed. 

In  calculating  the  time  of  the  propagation  of  the  wave  to  Batavia,  Mr.  Verbeek 
has  estimated  the  height  of  the  volcanic  wave  in  various  sections,  and  calculated 

his  speed  for  those  sections,  by  the  formula,  V=  a/ ^{^+€) (2  A+e),  where  g  iB 

gravity,  h  the  depth  of  water,  and  e  the  height  of  the  crest  above  the  normal  level 

of  the  water.     I  have  contented  myself  with  the  formula,  V=  ^gh.     My  result  for 

the  time  of  propagation  agrees  exactly  with  that  of  Mr.  Verbeeb:,  which  is  to  be 

accounted  for  by  the  different  routes  which  we  have  assumed  the  wave  to  take, 

among  the  numerous  islands  and  shoals,  and  also  by  the  different  depths  which  we 

have  calculated  for  the  various  sections ;  for,  though  I  have  styled  the  chart  excellent, 

the  bottom  is  so  uneven  that  any  attempt  to  arrive  at  a  very  accurate  estimate  of 

mean  depths  can  be  only  deceptive. 

To  Anjer  the  wave  would  have  taken  37  minutes,  to  Tyringin  30  minutes,  to 

Merak  45  minutes,  and  to  Telok  Betong  61  minutes. 

*  See  p.  69,  where  General  Strachey,  from  the  discussiou  of   several  barograph  diagrams,  arrives 
at  a  slightly  diflferent  conclusion. 


CAPTAIN  WHARTON   ON   THE   SEISMIC   SEA   WAVES. 


95 


Assuming  that  waves  were  generated  at  some  or  all  of  the  great  explosions 
registered  by  the  pressure  gauge  at  the  gasworks  at  Batavia,  the  following  table 
shows  the  time  of  arrival  of  such  waves  at  the  above  places  on  the  shores  of  the 
Strait  of  Sunda.  The  second  column  gives  the  measure  of  the  force  of  the  air  waves 
as  registered  by  the  pressure  gauge : — 


Air  wave  at  Batavia.                   ' 

Water  wave 
.    left 

Arrive 
at 

Arrive 
at 

Arrive 
at 

Arrive  at 

ExcMs  of  ladi- 

Barometric 
equivalent. 

Telok 

Time. 

.  catorreadinff 
above  estimated 
normal. 

Krakatoa. 

Tyringin. 

Anjer. 

Merak. 

Betong. 

h. 

m. 

mm* 

in. 

h.     m. 

h.     m. 

h,     m. 

h.     m. 

h.     m. 

26th— 17 

20 

13 

•08 

17     07 

17     37 

17     44 

17     52 

18     08 

27th—  1 

55 

20 

•12 

1     42 

2     12 

2     19 

2     27 

2     43 

2 

38 

21 

•12 

2     25 

2     55 

3     02 

3     10 

3     26 

4 

56 

22 

•13 

4    43 

6     13 

5     20 

5     28 

5    44 

5 

43 

41 

•24 

5     30 

6     00 

6     07 

6     15 

6    31 

6 

57 

41 

•24 

6    44 

7    14 

7     21 

7     29 

7    45 

..         9 

42 

29 

•17 

9     29 

9     59 

10     06 

10     14 

10    30 

„       10 

15 

63 

•37 

10    02 

10     32 

10    30 

10    47 

11     02 

„       11 

05 

40 

•23 

10     52 

11     22 

11     29 

11     37 

11     53 

We  have,  however,  records  only  of  certain  sea  waves,  which  may  be  connected 
with  some  of  the  air  waves. 
Thus— 


Air  wave  at  Batavia. 

Sea  wave  at 

At 

h.     m. 

26th-— 17    20  p.m.            

Tyringin. 

Between  18  and  19. 

Telok  Betong. 
Merak. 

19  or  19.30. 

27tli—  1     55  a.m.            

Sirik. 

"About"  1. 

„         5     43    „               ...         ... 

„        6     57    „               

Anjer. 

Telok  Betong. 

Anjer. 

„        6.30. 
Between  6  and  7. 
*' About*'  7.30. 

One  fact  in  connection  with  these  inundations  on  the  coasts  exposed  to  the  direct 
waves  from  Krakatoa  is  worthy  of  notice ;  and  that  is,  that  the  earlier  waves, 
though  of  no  insignificant  height,  were  partial.  Thus,  the  wave  between  18  hrs.  and 
19  hrs.  of  the  evening  of  the  26th  was  scarcely  noticed  at  Anjer,  although  on  the  same 
shore,  to  the  north  and  south,  considerable  damage  was  done.  The  village  of  Sirik, 
only  6  miles  from  Anjer,  was  destroyed  at  1  hr.  on  the  27th ;  but  this  wave  is  not 
mentioned  at  any  other  place. 

Krakatoa  stands  in  the  centre  of  the  Strait  of  Sunda,  the  shores  of  which  form 

a  rough  elongated  semi-ellipse.     The  outward,  or  western,  portion  of  the  ellipse  being 

absent,  permits  free  outlet  for  waves  in  that  direction  into  the  Indian  Ocean.     The 

eastern  smaller  end  of  the  ellipse  also  is  missing ;  and  permits  waves  to  travel  in  that 

direction  through  a  passage  12  miles  in  width. 

o  2 


96  CAPTAIN   WHARTON   ON   THE   SEISMIC   SEA   WAVES. 

To  the  west,  the  water  is  clear  and  deepens  regularly  to  the  Indian  Ocean  ;  as 
far  as  the  imperfect  nature  of  the  survey  admits  of  estimation. 

To  the  east,  the  water  is  comparatively  shallow :  a  large  island  blocks  the 
already  narrow  channel,  reducing  it  to  9 1  miles,  which  opens  into  the  stiU  shallower 
Java  Sea,  encumbered  with  reefs  and  shoals,  and  hemmed  around  by  the  far  extending 
islands  of  the  Eastern  Archipelago. 

To  the  west,  therefore,  the  waves  from  Erakatoa,  which  we  have  seen  were 
probably  50  feet  in  height  on  leaving  the  island,  have  freely  spread.  To  the  east, 
friction  among  the  shoals  has  rapidly  reduced  them  ;  so  that  their  extension  in  that 
direction  has  been  comparatively  small. 

The  indications  of  the  tide  gauge  of  the  harbour  of  Tanjong  Priok  at  Batavia 
are  most  valuable,  as  giving  the  nearest  and  most  unmistakable  record  of  the 
Krakatoa  waves,  A  glance  at  the  diagram  will  show  the  character  of  the  dis- 
turbance. 

From  20  hrs.  of  the  26th,  the  curve  begins  to  show  signs  of  oscillations  of  level, 
which  are,  however,  small  until  noon  of  the  27th,  not  averaging  more  than  3  inches. 
Notwithstanding,  waves  may  be  traced  corresponding  to  the  explosions  of  1  hr. 
42  mins.,  2  hrs.  25  mins.,  and  5  hrs.  30  mins.  of  the  27th,  of  which  the  best  marked  is 
that  corresponding  to  the  5  hrs.  30  mins.  explosion,  which  aiTived  at  Batavia  at 
8  hrs.  20  mins. 

At  11  hrs.  30  mins.  the  water  began  quickly  to  rise ;  and  at  12  hrs.  15  mins.  a 
perpendicular  line  shows  that  the  final  rise  was  almost  a  wall  of  water,  as  the  first 
great  wave  arrived  and  inundated  the  shore.  This  attained  a  height  of  7^  feet  above 
water  level  at  the  time,  at  12  hrs.  36  mins.  It  then  fell  as  rapidly  to  10  feet  below 
the  level.  These  measurements  are  those  given  by  Mr.  Verbeek,  who  states  that 
the  gauge  would  not  register  the  full  range  of  the  wave.  The  diagram  shows  only 
+  1*60  m.,  and  —  0*23  m„  but  Mr.  Vebbebk  states  that  the  measurement  for  high 
level  was  taken  on  the  stones  of  the  pier  as  +  2*35  m. 

That  for  low  level  he  gives  as  —  3*15  m.  The  gauge  would  register  —  1*10  m. ; 
but  Mr.  Yebbeek  gives  as  his  explanation  of  the  lower  minimum  which  he  adopts,  that 
the  water  had  already  begun  to  rise  under  the  influence  of  the  second  wave,  before 
the  level  could  fall  below  —  0*23  m.  It  is  not  easy  to  understand,  if  this  was  so, 
how  the  water  could  have  been  noted  at  —  3*15  m.,  and  the  shape  of  the  curve  does 
not  give  any  justification  for  the  assumption.  He  does  not  say  how  the  observations 
for  the  minimum  were  taken,  beyond  the  statement  that  they  were  made  to  fixed 
points  in  the  port.  This  figure  therefore  for  the  minimum  appears  doubtful,  and  I 
am  inclined  to  think  that  the  range  of  this  first  wave  cannot  be  considered  as 
very  exact,  and  is  probably  under  the  amount  given  by  Mr,  VEltB]BEK,  which  is 
18  feet. 

The  second  wave  als9  was  above  the  highest  point  the  gauge  would  mark,  and 
may  be  taken  as  Mr.  Verbeek  gives  it,  1'95  m.     This  wave  attained  its  maximum  at 


CAPTAIN  WHARTON   ON  THE   SEISMIC  SEA  WAVES.  97 

14  hrs.  48  mins.,  or  2  hra.  12  mins.  after  the  first.  Its  crest  was  therefore  80  miles 
distant  when  the  first  wave  arrived. 

It  is  to  be  remarked  that  at  Batavia  the  first  phenomenon  was  a  rise  unpreceded 
by  any  faU  of  level,  which  appears  to  indicate  that  the  wave  leaving  Krakatoa  was 
a  positive  one. 

The  first  wave  is  followed  by  waves  of  gradually  diminishing  height,  14  of  which 
are  at  tolerably  regular  intervals,  and  give  a  mean  period  of  2  hrs.  02  mins.  from  crest 
to  crest.     These  are  : — 

h.     m.  h.      m.  h.      m.  H.      m.  h.      m.  lu     m.  h.    m. 

Times   ..     12  36   14  48   16  43   18  58   20  25   22  20   0  40 

b.    m.  li.    m.  H.    m.  h.    in.  h.    m.  h.    m.  h,    m. 

Intervals..  2   12         1  55         2  15         1  27         1  55         2  20         2  30 

Height  in  feet*      6^  i^  If  1^  i  1^  1 

b.   m.         h.    m.        b.    m.         b.    m.  b.     m.  b.     m.  b.    m.  b.     nu 

Times   ..     3  10   5  10   7  20   9  10   11  00   13  10   14  55   17  05 

b*    m*         b*    in*  b»    m*  b.    m.  b.    m.  b.    m.  b.    nu 

Intervals  ,.  2  00       2  10       1  50         1  50         2  10         1  45         2  10 

Height  in  inches     91194  4  2  3  3 

This  period  of  2  hrs.  02  mins.  is  very  reiTiarkable  if  the  circumstances  are  con- 
sidered. If  the  wave  was  caused  by  any  sudden  displacement  of  the  water,  as  by 
the  falling  of  large  masses  of  ejected  m^^tter,  and  huge  fragments  of  the  missing 
portions  of  Krakatoa,  or  by  the  violent  rush  of  st§am  from  a  submarine  vent  through 
the  water,  it  is  hardly  to  be  conceived  that  two  hours  would  elapse  before  the 
following  wave,  the  second  of  the  series,  started  after  it. 

K  the  supposition  that  the  wave  was  caused  by  the  opening  of  a  great  chasm  in 
the  earth,  by  the  bursting  of  the  si4es  of  the  hollowed  Krakatoa,  into  which  the  sea 
rushed,  cpuld  be  inaintained,  a  wave  of  long  period  might  also  be  explained  ;  but, 
though  some  such  inrush  must  have  occurred  when  the  water  flowed  over  the  site  of 
the  island,  to  set  up  a  long  wave,  as  is  now  recjuired,  two  things  appear  necessary  : 

First, — that  the  chasm  was  large  enough  to  permit  water  to  flow  into  it  con. 
tinuously  for  an  hour  at  a  rate  sufficiently  rapid  to  cause  a  great  lowering  of  the 
water  level  in  the  vicinity  of  the  island,  in  prder  to  set  up  a  wave. 

Secondly, — that  the  first  effect  reaching  the  shore  was  a  negative  wave. 

Now,  the  first  supposition  is  so  improbable  that  it  certainly  requires  evidence 
before  it  can  be  adopted ;  and  the  second  is  contrary  to  the  record  of  the  Batavi^ 
gauge,  which  shows  a  distinct  positive  wave  as  the  earliest  phenomenon. 

If,  however,  upheaval  of  the  bottom  of  the  sea,  more  or  less  gradual,  and  lasting 

^  These  heights  are,  as  all  others  of  waves  in  this  Part,  measured  from  the  normal  level  ot  the 
water  At  the  time,  as  deduced  from  the  tidal  diagrams. 


98  CAPTAIN   WHARTON  ON  THE   SEISMIC   SEA  WAVES. 

for  about  an  hour,  took  place,  we  should  have  a  steady  long  wave  flowing  away  from 
the  upheaved  area,  which  as  it  approached  the  shore  would  be  pUed  up  considerably 
above  its  normal  height.  Thus  these  waves  of  long  period  would  be  set  up ;  and 
this  would  also  account  for  the  rapid  current  recorded  by  the  ship  "  William  H. 
Besse/'  which  is  described  as  10  miles  an  hour,  though  probably  that  is  au 
exaggeration.     The  water  would  flow  back  on  the  motion  ceasing. 

If  we  now  turn  to  the  condition  of  the  area  round  Erakatoa  and  compare  it 
with  the  previous  state  of  things,  we  find  that,  as  summarized  at  page  92,  upheaval 
has  taken  place  over  a  large  surface.  Two  entire  islands  have  appeared  where 
formerly  the  water  was  deep.  Verlaten  Island  has  been  increased  by  two  square 
mQes,  and  extensive  banks  have  been  raised. 

I  should  have  been  inclined  to  consider  this  as  the  sole  caiise  of  the  great  waves, 
more  especially  as  it  would  entirely  explain  the  somewhat  remarkable  &Lct  that  ships 
not  far  from  the  volcano  at  the  time  the  wave  was  travelling  from  it,  felt  nothing  of 
the  stupendous  undulation  which  rushed  so  far  up  the  slopes  of  the  hills. 

We  find,  however,  as  wQl  be  seen  when  the  eye  observations  at  distant  places 
are  Considered,  that,  besides  the  waves  of  long  period,  which  after  travelling 
thousands  of  miles  were  not  of  sufficient  height  to  attract  much  notice,  waves  were 
observed  by  eye-witnesses  following  one  another  at  rapid  intervals  of  from  five  to 
fifteen  minutes,  and  of  heights  of  from  two  to  three  feet,  though,  from  their  short 
duration,  they  were  not  marked  upon  the  gauges. 

These  seem  to  demand  another  cause,  and  it  appears  to  me  that  they  may  be  due 
to  the  large  masses  of  the  island  blown  away  by  the  force  of  the  explosions  and 
falling  into  the  sea,  or,  possibly,  to  the  sudden  displacement  of  the  water  over  a 
submarine  vent. 

The  missing  mass  of  Ki*akatoa  may  be  roughly  estimated  to  be  at  least  two  hundred 
thousand  million  cubic  feet  (200,000,000,000).  A  fiftieth  part  of  this  mass  dropping 
suddenly  into  the  water  would,  by  its  displacement  alone,  furnish  sufficient  liquid  to 
form  a  wave  circle  of  100  miles  in  circumference,  20  feet  high,  and  350  feet  wide. 
The  surrounding  islands  and  shoals  would,  however,  prevent  a  perfect  circle  being 
formed,  and  the  wave  might  therefore  be  concentrated  on  certain  parts  of  the  arc,  and 
be  at  some  places  higher  than  at  others,  varying  according  to  the  direction  in  which 
the  masses  fell.     It  has  been  remarked  that  this  partiality  of  the  waves  was  noticed. 

I  incline  then  to  the  opinion  that  the  destructive  waves  in  the  Strait  of  Sunda 
were  mainly  due  to  these  masses  falling  into  the  sea,  or  to  sudden  explosions  under 
the  sea  after  it  flowed  freely  over  portions  of  the  former  site  of  the  island,  possibly  to 
both  causes ;  but  that  the  long  wave  which  was  recorded  on  so  many  tide  gauges  had 
its  origin  in  upheaval  of  the  bottom. 

It  does  not  appear  unreasonable  to  assume  that  at  tha  time  of  the  great 
explosion  of  10  o'clock,  waves  of  both  characters  would  be  more  or  less  synchronously 
formed. 


CAPTAIN    WHARTON   ON   THE   SEISMIC   SEA  WAVES. 


99 


I  advance  this  hypothesis  of  the  origin  of  the  waves  with  some  diffidence,  but 
it  appears  to  me  not  improbable  from  the  known  facts,  and  it  would  explain  away 
some  difficulties. 

I  cannot  find  any  accurate  observations  bearing  on  the  subject  of  the  descriptions 
and  heights  of  waves  originating  from  a  violent  displacement  of  water  on  a  large 
scale. 

Two  explosions  have  recently  (October,  1886)  taken  place  at  Spithead.  The 
first  of  6,000  lbs.  of  gun-cotton  in  10  fathoms  water  occurred  on  a  very  calm  day. 
Ujafortunately  I  knew  nothing  of  it  beforehand,  and  no  one  was  on  the  look  out  for 
waves.  Two  officers,  however,  standing  on  the  beach  4^  miles  distant,  noticed  a  wave 
approaching,  and  estimated  its  height  at  about  two  feet.  It  was  followed  by  others  at 
short  intervals,  but  the  number  was  not  noted. 

The  tide  gauge  in  Portsmouth  Harbour,  a  very  delicate  instrument  by  Sir 
William  Thomson,  showed  on  its  diagram  no  disturbance.  The  distance  is  4  miles, 
but  shoals  and  a  narrow  channel  intervene,  which  possibly  killed  the  wave,  otherwise 
this  failure  to  mark  the  wave  might  be  taken  as  evidence  that  these  short  waves  did 
not  afiect  the  gauge. 

The  second  explosion  of  six  mines  of  500  lbs.  of  gun-cotton  each,  45  feet  below 
the  surface  in  60  feet  of  water,  took  place  on  5th  November,  1886.  The  mines  were 
laid  in  a  line  about  100  feet  apart.  The  day  was  stormy,  and  the-  surface  of  the  sea 
much  troubled. 

The  explosion  threw  up  a  wall  of  water  extending  a^long  the  line  of  mines,  and 
estimated  to  be  150  feet  high. 

Only  one  observer  on  shore  recorded  any  waves.  He  had  provided  himself  with 
a  small  tube,  in  which  a  float  carrying  a  light  rod  worked.  The  float  worked 
incessantly  from  the  action  of  the  short  wind  waves,  but  he  noticed  that  the  whole 
body  of  the  surface  was  raised  at  regular  intervals.  As  his  float  hung  at  a  certain 
point  when  falling,  he  was  not  able  to  register  the  depressions  by  it,  but  the  observa- 
tions for  the  crests  were  as  follows  : — 


Explosion  at 
Crest  at 


h. 

m. 

•   8, 

15 

35 

20 

20 

22 

30 

25 

00 

27 

45 

29 

45 

31 

30 

34 

00 

Interyals. 

m.' 

0. 

4 

45 

2 

10 

2 

30 

2 

45 

2 

oo: 

1 

45 

2 

30 

The  height  fix)m  crest  to  trough  he  estimates  at  one  foot. 

The  first  wave  arrived  at  4  mins.  45  sees,  after  the  explosion,  the  site  of  which 


100 


CAPTAIN  WHARTON  ON   THE   SEISMIC   SEA  WAVES. 


was  1-j^  miles  distant.     The  intervening  mean  depth  is  6  fathoms.     Theory  gives  a 
time  of  4  mins.  12  sees,  to  traverse  this  distance. 

It  is  to  be  remarked  that  the  observer  had  no  pre-conceived  ideas  as  to  the  time 
the  wave  should  arrive.  His  observations  are  therefore  quite  independent.  He 
reports  that  the  first  phenomenon  was  a  fall  in  the  surface  immediately  followed  by 
the  first  crest. 


Genebal  Account  of  Data  available,  and  the  Mode  of  theib  Discussion. 

To  follow  the  movements  of  the  wave  which  spread  to  distant  shores,  we  have 
the  indications  of  self-registering  tide  gauges  and  eye  observations.  The  former  only 
can  be  considered  as  accurate,  but  in  some  cases  the  latter  give  fair  results*  The 
tidal  diagrams  available  are  as  follows  : — 


To  the  west  of  Exakatoa — 
Andaman  Islands 


East  coast  of  Hindostan 


In  River  Hoogly  • . 

West  coast  of  Hindostan 

South  coast  of  Arabia    •  • 

South  coast  of  Africa     . . 

South  Georgia  Island     . . 

Tierra  del  Fuegp 

East  coast  Central  America 

West  coast  of  France    • . 
North  coast  of  France  , . 


South  coast  of  England. . 


Port  Blair. 
T^egapatam. 

Madras. 

Vizagapatam. 

False  Point. 
^  Dublat. 
f  Diamond  Harbour. 
I  Kidderpore 

{Beypore. 
Bombay. 
KarachL 
Aden, 
r  Port  Alfred. 
. .  i  Port  Elizabeth, 
I  Table  Bay. 
Moltke  Harbour. 
Orange  Bay. 
Colon. 
rSocoa. 
L  Rochefort. 

{Cherbourg. 
Havre. 
.  Devonport. 
Portland. 
Portsmouth. 
^  Dover. 


CAPTAIN  WHARTON   ON   THE   SEISMIC    SEA  WAVES. 
To  the  east  of  Krakatoa — 


101 


North  and  East  coasts  of  Java. .  ^ 

South  coast  of  Australia 

New  Zealand 

Ed^t  coast  of  Australia . . 
Sandwich  Islands 
xxjasisLa      •  •  •  •  •  • 

West  coast  of  North  America 


Batavia  (Tandjong  Priok). 

Ujong  Pangka. 

Sourabaya. 

Karang  Kleta. 
rPort  Adelaide. 
LWilliamstown. 
r  Port  Lyttelton. 
L  Dunedin. 

Sydney. 

Honolulu. 

St.  Paul's,  Kodiak. 

Saucelito,  San  Francisco. 


Of  eye  observations,  we  have  reports  to  the  west  of  Krakatoa  from — 


West  coast  of  Sumatra  . . 
South-west  coast  of  Ceylon 

East  coast  of  Ceylon 

Seychelles  Islands 
Cargados  Garajos 
Rodriguez  Island 
Mauritius 

To  the  east  of  Krakatoa,  from — 
West  coast  of  Australia 
New  Zealand      •• 


Padang. 
rCalle. 
'   L  Colombo. 
f  Arugam. 

Batticaloa. 

Trincomalee. 

Mullaittivu. 
t  Point  Pedro. 

Mah^. 

Avocaire  Island 

Mathurin  Bay. 

Port  Louis. 


r  Cossack. 
LGeraldton. 
Various  places. 


Throughout  this  paper  the  following  is  the  sense  of  diflferent  terms : — 

The  height  of  the  wave  is  the  height  of  the  crest  above  the  normal  level  of  the 

water  at  the  time. 
The  range  of  the  wave  is  the  vertical  distance  from  crest  to  trough. 
The  length  or  amplitude  of  the  wave  is  the  distance  in  geographical  miles  from 

crest  to  crest. 

The  original  diagrams  from  the  automatic  gauges  are  on  every  conceivable  scale, 
for  both  height  and  time.     Some  are  kept  in  civil,  some  in  astronomical,  time  ;  some 


102  CAPTAIN   WHARTON   ON   THE   SEISMIC   SEA  WAVES. 

record  the  height  in  mHres,  some  in  feet ;  some  work  from  left  to  right,  others  in  the 
opposite  direction. 

The  copies  accompanying  this  paper  are  reduced  to  one  uniform  scale,  convenient 
for  publication,  of  ^  of  an  inch  to  a  foot,  and  ^  of  an  inch  to  the  hour,  except  the 
curves  for  Socoa,  Rochefort,  Cherbourg,  and  Havre,  which  are  on  a  larger  scale,  so 
that  the  minute  fluctuations  may  remain  visible.  These  show  the  heights  in  feet,  at 
local  civil  time,  counting  from  midnight  to  24  hours.  (See  Plates  XVII.  to  XXXV., 
p.  150.) 

In  calculating  the  time  of  translation  in  the  tables  I  have  reduced  all  the  times 
to  Greenwich  civil  time ;  but  in  speaking  of  the  waves,  I  mention  the  local  tima 

The  indications  of  the  arrival  of  the  wave  on  these  diagrams  are  by  no  means 
always  precise ;  and  the  variety  in  the  appearance  of  the  diagrams  is  very  marked. 
In  all  cases  they  show  long  continued  disturbance  ;  but  the  complication  of  the  waves 
in  some  is  as  remarkable  as  the  regularity  of  the  series  is  in  others.  In  all  cases  the 
more  prominent  waves  are,  unlike  those  registered  at  Batavia,  preceded  by  minor 
oscillations,  which  in  some  instances  merge  so  insensibly  into  the  higher  waves  that  it 
is  difl&cult  to  identify  any  one  wave  as  the  first  of  what  may  be  called  by  comparison 
the  greater  disturbance. 

Seeing  that  several  large  waves  reached  the  shores  of  Sunda  Strait  before  the 
great  one  of  10  o'clock,  it  would  not  be  surprising  to  find  that  these  earlier  waves 
occur  on  the  diagrams,  were  it  not  for  the  very  slight  indications  of  them  marked  on 
the  Batavia  gauge.  The  path,  however,  to  the  westward  is  so  much  more  open  that 
these  possibly  shorter  waves  found  their  way  across  the  Indian  Ocean,  while  they 
were  killed  by  the  sudden  expansion  into  the  Java  Sea. 

On  the  east  coast  of  India  the  arrival  of  the  greater  disturbance  is  unmis- 
takable ;  which  is  probably  due  to  the  shorter  distance  and  the  unimpeded  course  of 
the  waves  in  deep  water.  Here  also  there  appears  to  be  but  one  series  of  the  larger 
waves  for  at  least  some  hours ;  but  at  places  further  removed,  several  series  of  long 
waves  can  be  made  out,  which  much  interfere  with  the  regularity  of  the  diagrams. 

The  position  of  some  of  the  gauges,  inside  bars,  up  rivers,  and  in  similar  places 
not  open  to  free  access  from  the  sea,  may  have  had  some  effect  on  the  appearance  of 
the  diagrams. 

Another  cause  of  variety  is  the  difference  in  the  construction  of  the  gauges. 
When  the  orifices  in  the  tube  which  admit  the  water  are  too  large,  local  waves  appear 
to  affect  the  record. 

Assuming  fi-om  the  well-marked  character  of  the  waves  shown  on  the  Batavia 
diagram  that  the  period  of  the  waves  that  left  Krakatoa  was  about  2  hours,  I  have,  in 
my  investigation  of  the  diagrams,  first  examined  them  to  see  whether  the  same  period 
can  be  identified.  In  this  I  have  met  with  imperfect  success.  Though  in  many  cases 
such  a  period  can  be  found,  it  is  fi-equently  only  to  be  arrived  at  by  taking  every 
alternate  wave,  the  intermediate  ones  being  nearly  half-way  between  those  selected.    It 


CAPTAIN   WHARTON   ON  THE   SEISMIC   SEA   WAVES.  103 

thus  appears  either  as  if  the  original  waves  had  in  their  long  course  divided  and 
doubled  themselves,  or  as  if  the  great  wave  reflected  from  the  eastern  shores  of  the 
land  bounding  the  Strait  of  Sunda  was  the  cause  of  the  intermediate  waves,  the 
distance  of  these  shores  being  such  as  would  cause  the  time  elapsing  between  the 
primary  and  reflected  waves  to  be  roughly  a  moiety  of  the  long  period  of  122  minutes 
recorded  at  Batavia. 

At  the  very  distant  stations,  as  Orange  Bay,  and  the  ports  of  the  English 
Channel,  the  wave  period  is,  in  some  instances,  roughly  one-fourth  of  the  original 
period  of  Batavia ;  which  looks  like  a  still  further  sub-division  of  the  waves ;  but 
there  are  exceptions. 

In  all  cases  I  have  taken  the  first  of  a  recognisable  series  of  higher  waves  as 
being  identical  with  the  great  10  o'clock  wave  from  Krakatoa,  though  generally  the 
maximum  wave  follows  at  a  longer  or  a  shorter  interval. 

The  speeds  that  are  tbus  deduced  should  be,  therefore,  those  of  the  great  wave  ; 
the  previous  undulations,  though  sometimes — as  far  as  height  is  concerned — ^merging 
somewhat  insensibly  into  the  accepted  waves,  not  agreeing  with  them  in  period. 
The  speed,  moreover,  that  would  correspond  with  these  earlier  waves  in  most  of  the 
diagrams  would  be  so  high  as  to  place  them  beyond  the  bounds  of  probability. 

I  have  given  the  speed  calculated  from  the  formula  V  =  v^  grA,  and  the  corre- 
sponding depth  in  fathoms  of  the  water  over  which  the  wave  has  travelled,  as  well 
as  the  probable  mean  depth  from  the  known  soundings  on  the  line. 

A  direct  comparison  can  thus  be  made  between  the  theory  and  the  known  facts ; 
and  although  the  soundings  obtained  are  in  some  cases  scanty,  and  in  others  altogether 
wanting,  it  will  be  seen  that  in  such  instances  where  material  exists,  the  comparison 
is  always  to  show  that  the  wave  has  travelled  at  a  slower  velocity  than  theory 
demands.  Against  this  conclusion  must  be  stated  the  consideration  that  any  unknown 
ridges  would  diminish  the  speed  ;  but  these  must  be  large,  or  the  portion  of  the  wave 
overlapping  them  would  still  travel  at  the  speed  due  to  deeper  water,  and  over  a  very 
slightly  longer  course. 

It  will  be  seen  that  the  first  great  wave  is  sometimes  preceded  by  a  considerable 
fall,  or  negative  wave.  From  the  fact  of  the  Batavia  gauge  showing  as  the  first 
indication  an  unmistakable  sharp  rise,  I  conclude  that  the  original  disturbance 
propagated  from  Krakatoa  was  a  positive  wave,  and  that  this  depression  is  merely  due 
to  the  fact  of  smaller  waves  preceding  the  greater  disturbance,  whatever  may  have 
been  the  reason  of  their  existence. 

In  the  discussion  of  each  diagram,  I  have  given  the  period  of  the  series  of  waves, 
both  of  those  which  seem  to  correspond  with  the  two-hour  period,  and  of  the  shorter 
series  of  which  these  are  made  up. 

I  have  presented  in  a  tabular  foi-m  the  main  results  of  the  investigation  into  the 
time  of  translation  of  the  distiurbance. 

To  arrive  at  the  most  probably  accurate  estimate  of  the  velocity  of  the  wave 

P  2 


104  CAPTAIN   WHARTON    ON  THE    SEISMIC   SEA  WAVES. 

between  Krakatoa  and  the  different  places^  I  have  taken  from  the  large  scale  charts 
of  each  harbour  and  coast,  when  sufficient  data  are  forthcoming,  the  distances  over 
which,  in  approaching  the  tide  gauge,  the  wave  would  have  to  travel  in  shallow  water, 
that  is,  water  under  1,000  fathoms. 

For  these  distances  I  have  calculated  the  time  which  the  wave  would  occupy  in 
traversing  them,  according  to  the  depths,  by  the  formula  V=  "^'gh^  and  subtracting 
this  time  and  distance  from  the  total,  the  remainder  will  give  the  time  taken  by  the 
wave  in  crossing  the  deeper  intervening  space.  This  gives  a  better  means  of  judging 
whether  the  disturbance  can  be  considered  truly  to  have  emanated  from  the  volcano, 
as  the  smaller  depths,  in  which  the  change  of  velocity  is  most  rapid,  are  thereby 
eliminated. 

Unfortunately,  in  many  instances  the  soundings  are  not  carried  far  enough  from 
the  shore  to  show  where  the  1,000  fathom  line  is. 

In  one  of  the  columns  in  the  table  I  give  the  outermost  soundings  available. 

It  is  to  be  regretted  that  at  the  outset,  from  Krakatoa  itself,  the  soundings  are  so 
sparse  that  it  cannot  be  determined  with  any  exactitude  where  the  1,000  fathom 
depths  begin,  but  I  have  taken  it  as  50  miles  from  the  island,  and  have,  from  the  few 
depths  given,  calculated  16  minutes  as  the  probable  time  when  the  wave  would  reach 
this  depth,  and  henceforth  travel  in  deeper  water  over  the  Indian  Ocean.  I  have 
therefore  subtracted  this  50  miles  and  these  16  minutes  from  the  distances  and  times 
of  every  wave  leaving  Krakatoa  by  the  west. 

The  distances  have  been  in  all  cases  taken  as  the  shortest,  i.e.,  have  been 
measured  on  a  great  circle,  or  on  several  arcs  of  great  circles,  when  land,  islands,  or 
banks  intervene. 

Though  Sir  G.  Airy,  in  his  article  in  the '  EncyclopsBdia  Metropolitana,'  states  that 
it  is  only  when  the  amplitude  of  the  wave  is  one  thousand  times  the  depth  of  the 
water  that  the  simplified  form  V  =  *y  gh  of  his  general  equation  can  be  taken  as 
accurate  ;  the  difference  between  the  depths  thus  calculated  and  those  by  the  more 
nearly  exact  equation,  is  so  small,  when  dealing  with  these  waves  which  appear  to 
have  an  amplitude  of  over  one  hundred  times  the  depth,  that,  considering  the 
inexactness  of  the  times  and  the  doubt  as  to  the  identification  of  the  right  wave,  I 
have  used  the  simpler  form. 

To  the  eastward  of  Krakatoa,  or  into  the  Java  Sea,  the  wave  does  not  appear  to 
have  been  noticed  at  any  great  distance.  Thanks  to  the  tide  gauges,  three  in  number 
— erected  in  the  Strait  of  Sourabaya — indications  of  its  presence  there  exist ;  but 
its  maximum  height  is  only  10  inches,  too  insignificant  a  disturbance  to  be  otherwise 
noticed. 

We  do  not  find  that  it  was  observed  beyond  Sourabaya,  which  is  440  miles  from 
Krakatoa. 

To  the  great  and  sudden  expansion  of  the  area  in  which  the  wave  would  find  itself 
on  emerging  from  the  narrow  portion  of  the  Strait  of  Sunda,  north  of  Merak  ;  to  the 


CAPTAIN  WHARTON   ON   THE   SEISMIC    SEA   WAVES.  105 

general  shallowness  of  the  Java  Sea  ;  and  to  the  interposition  of  banks  and  islands,  is 
doubtless  due  this  small  extension  of  the  disturbance  to  the  east  and  north. 

The  automatic  tide  gauge  at  Singapore  showed  no  disturbance,  nor  was  anything 
remarked  at  Hong  Kong. 

The  wave  at  Merak  was,  say,  actually  50  feet  high,  having  travelled  over  an 
average  depth  of  29  fathoms  for  34  miles. 

Up  to  this  point,  however,  the  sea  is  open,  and  no  interference  by  reflection  or 
otherwise  would  take  place ;  but  a  gradual  closing  of  the  passage  towards  the  end 
would  probably  tend  to  raise  its  height. 

Immediately,  however,  after  passing  the  strait,  10  miles  wide,  on  one  side  of 
which  Merak  is  situated,  the  height  of  the  wave  must  have  rapidly  diminished  on  its 
expansion  in  the  Java  Sea.  Thus  we  find  at  the  North  Watcher,  a  small  island  in 
the  open  sea,  53  miles  beyond  Merak,  and  82  miles  from  Krakatoa,  that  its  height 
was  reduced  to  8  feet,  as  reported  by  the  lighthouse  keepers  in  the  island.  The 
average  depth  over  which  the  wave  would  travel  from  Krakatoa  to  the  North  Watcher 
is  22  fathoms,  the  course  being  nearly  in  a  straight  line.  At  Dindang,  240  miles 
from  Krakatoa,  the  wave  was  4^  feet  high,  having  travelled  in  a  straight  line  over 
an  average  depth  of  16  fathoms.  The  same  is  found  in  the  other  direction  jfrom 
Krakatoa.  At  Vlakke  Hoek  Lighthouse,  54  miles  in  a  straight  line  from  Krakatoa, 
the  water  rose  50  feet ;  but  at  Benkunat,  36  miles  further — ^but  round  the  corner — ^it 
was  barely  noticed. 

Table  I.  gives  the  statistics  for  the  places  near  Krakatoa,  and  Plate  XXXIV. 
will  show  their  positions  better  than  any  description.  The  height  of  waves  must, 
however,  be  regarded  as  only  approximate,  as  they  are  all  from  eye  observations 
and  reports  only. 


106 


CAPTAIN   WHAETON  ON   THE   SEISMIC   SEA  WAVES. 


TABLE  I. 
Showing  height  of  wave  in  the  immediate  vicinity  of  Sunda  Strait. 


Time 

from 

Krakatoa. 


o 


-3. 

OQ 


I 


I 


I 

o 
OQ 


^Tyringin 

Anjer 

Merak 

Kalianda     •  • 

Telok  Betong 
^Vlakke  Hoek 

North  Watcher  Id 

Tjabang 
Dindang 

'Bantam 


Lontar 
Kramat 
Batavia  (T.  Prick) 
TjilintiDg    . . 
Tji  Lamaja 
Bambatan  . . 
Japara 

Ujong  PaDgka 

^Winkoops  Bay 

Tyliatiap     • . 

Benkunat    . . 


Kro6 
Sambat 
Manna 
Pino. . 

Bencoolen  . . 
Moeko-Moeko 
Painan 
^Padang 


2 
2 

4 

6 

8 

10 


00 


30 


30 


30 
30 
30 
00 
00 
32 


00 


Distance 
in 
sea  or 
geogra- 
phical 
miles.* 


46 


24 
26 
33 
27 
38 
54 
82 

95 

240 

50 


55 
77 
100 
102 
145 
184 
310 
440 
147 
330 
90 

130 
160 
210 
215 
265 
370 
455 
490 


Ayerage 
depth  in 
fathoms. 


29 
31 
29 
21 
17 
100 
22 

17 
16 

26 


27 

28 

28 

25 

22 

17 

26 
200 
200? 
300? 

300? 
350? 
350? 
350? 
300? 
300? 

? 

? 


Height 
of  wave 
in  feet. 


50? 
50? 
50? 
50? 
50? 
50? 
8 

4 


n 
11 

6 
2 


5 

6 
very- 
slight, 
none. 

6 

8 

7 

3 

4 

9 


Situation  as  regards  free  access 
for  wave. 


In  open  sea  in  straight  line  from 

Krakatoa. 
Open,  but  I'eefs. 
Open,  bnt  reefs,  in  stright  line  from 

Krakatoa. 
Only  15  miles  round  the  peninsula  of 

Merak,  where  the  wave  was  50 

feet. 
Open. 
Open. 

Open,  but  many  reefs. 
Close  to  east  of  Batavia,  but  protected. 
Open  bay,  but  screened  to  west. 
Open. 
Open. 
Open. 
Open. 

Fairly  open. 
30  milesroundcomerof  Ylakke  Hoek. 

60  milesroundcomerof  YlakkeHock. 

Open  to  wave. 

Bay  protected  from  direction  of  wave. 

5  miles  from  Mann&,  bnt  exposed. 

Protected  by  reefs. 

Open  to  wave. 

Bottom  of  bay  open  to  wave. 

Open  to  wave,  but  many  reefs. 


*  An  average  geographical  or  sea  mile  is  2,025  yards,  or  about  1  *  15  English  mile. 


CAPTAIN  WHARTON   ON   THE  SEISMIC   SEA  WAVES.  107 

TIDAL    DIAGRAMS. 


JAVA. 

There  are  three  automatic  tide  gauges  east  of  Batavia,  all  in  the  island 
of  Java. 

Ujong  Pangha. 

This  is  on  the  north  coast  of  Java,  340  miles  east  of  Batavia.  The  tide  gauge 
shows  disturbaDce  of  an  irregular  character,  in  which  no  period  can  be  recognised. 
A  small  wave  occurs  at  17  hrs.  45  mins.,  but  a  decided  rise  is  shown  at  21  hours, 
which  I  take  to  be  the  great  wave.  Its  height  is  about  9  inches.  This  time  will 
give  a  velocity  of  42  miles  an  hour,  which  agrees  almost  exactly  with  that  deduced 
from  the  formula  V  =  ^yh.  The  depths  from  off  Batavia,  up  to  which  spot  the 
track  of  the  waves  to  the  two  places  is  identical,  average  about  25  fathoms,  but 
vary  considerably.     The  disturbance  lasts  19  hours. 

It  is  rather  astonishing  that  the  regular  waves  which  are  registered  at  Batavia 
should  have  entirely  disappeared  by  the  time  the  disturbance  reached  this  gauge. 
The  long  extent  of  shallow  water  and  the  strong  currents  which  frequently  prevail 
off  this  coast  may  account  for  the  breaking  up  of  the  regularity. 

Ujong  Sourahaya, 

This  gauge  is  placed  on  a  point  half-way  through  the  narrow  and  shallow  strait 
of  Sourabaya.  The  disturbance  is  as  slight  and  irregular  as  at  Ujong  Pangka,  and  I 
take  the  first  distinct  wave  crest  at  22  hrs.  25  mins.  for  comparison. 

The  distance  from  Ujong  Pangka,  which  stands  at  the  entrance  of  the  strait,  is 
25  miles,  with  an  average  depth  of  i^  fathoms. 

This  should  require  1  hr.  36  mins.  to  traverse,  whereas  the  time  registered  is 
1  hr.  24  mins. — a  very  close  agreement  when  the  circumstances  of  the  channel 
are  considered. 

Karang  Kleta. 

This  gauge  is  on  a  small  rock  at  the  southern  end  of  Sourabaya  Strait.  The 
disturbance  is  again  irregular,  but  bears  a  marked  resemblance  to  Sourabaya,  from 
which  it  is  distant  14  miles,  with  an  average  depth  of  4  fathoms.  The  wave  which 
corresponds  to  that  at  Sourabaya  is,  however,  registered  25  minutes  earlier  than  at 
that  place,  which  makes  it  to  have  travelled  over  the  strait  from  Ujong  Pangka  in  an 
hour,  instead  of  2  hrs.  27  mins.,  which  is  given  by  theory.  Tliis  discrepancy  is  not 
easy  to  explain. 


108  CAPTAIN   WHARTON   ON  THE   SEISMIC   SEA  WAVES. 

INDIA. 

The  report  furnished  in  December,  1883,  by  Major  Baird,  R.E.,  in  charge  of  the 
tidal  survey  of  India,  has  been  already  communicated  to  the  Royal  Society.* 

The  account  of  the  disturbance  at  each  tidal  station  in  India,  as  taken  from  the 
original  diagrams,  is  given  in  great  detail,  and  all  the  interesting  points  are  discussed 
by  Major  Baird.  His  report  also  contains  statements  of  the  phenomena  noticed  at 
other  places  where  no  gauge  was  at  work. 

We  now  possess  much  fuller  information  on  many  of  the  occurrences  external 
to  India  than  was  available  when  Major  Baird  wrote  his  paper;  and,  with  the 
consent  of  the  Committee,  I  do  not  purpose  to  reproduce  the  paper,  as  it  would  be 
difficult,  without  destroying  its  connected  character,  to  remove  those  portions 
which  are  founded  on  insuflSicient  data. 

I  have  re-discussed  the  data  furnished  by  the  Indian  gauges  from  a  somewhat 
different  point  of  view  from  that  adopted  by  Major  Baird,  founding  my  selection  of 
waves  on  the  small-scale  diagrams  ftirnished  by  him,  and  checking  the  times  of 
arrival  of  the  waves  by  his  detailed  account,  taken  from  the  originals  as  given  in 
his  paper. 

Port  Blair. 

This  bay  in  the  Andaman  Islands,  1,480  miles  from  Krakatoa,  is  the  nearest 
place  furnished  with  a  gauge  to  the  west  of  the  Strait. 

From  3  hours  of  the  27  th  a  very  small  oscillation  is  shown,  which  increases  at 
noon ;  and  at  13  hrs.  55  mins.  a  very  distinct  wave,  with  a  height  of  7  inches,  appears. 

This  is  the  first  of  a  long  series  given  below — 

h.      m.  h.      m.  h.      m.        '  h.      m.  h.      m.  h.      m. 

Times        ..      13  55       14  53      16  03       17  09      18  05      19  14 


Intervals  .  . 

m.                   m.                  m.                   m. 

58             70            66             56 

m. 

69 

m. 

48 

Times 

20  02      21   12      22  35       23  15 

0  12 

1  20 

Intervals   . . 

70             83            40            57 

68 

55 

Times 

2  15        3  15        4  30        5  30 

6  40 

7  35 

Intervals  . . 

60             75             60            70 

55 

The  double  intervals  are — 

128     122     117     153     97     123     135     130  minutes. 

This  gives'  a. mean  interval  of  62  minutes,  or,  for  every  other  wave,  of  2  hrs. 
06  mins. — ^nearly  the  Batavia  interval. 

Taking  the  13  hrs.  55  mins.  wave  for  comparison,  the  velocity  for  the  distance 
of  1,480  miles  is  308  miles  an  hour  from  shore  to  shore.     Unfortunately,  in  this  case, 

•  *  Proc.  Roy.  Soc.,'  vol.  xxxvi.,  pp.  248-253. 


CAPTAIN   WHARTON   ON  THE    SEISMIC   SEA  WAVES.  109 

no  data  exist  for  eliminating  the  wave  near  the  Andaman  shore,  but  the  wave  has 
probably  travelled  at  about  320  miles  an  hour,  which  would  give  a  mean  depth 
of  over  1,500  fathoms. 

Negapatam. 

The  position  of  this  gauge  is  just  inside  the  bar  of  the  river,  but  the  coast  is 
straight  and  open.  The  diagram  shows,  as  at  Port  Blair,  a  small  oscillation  from 
midnight  to  13  hours  of  the  27th,  when  a  distinct  wave  of  9  inches  in  height  is 
registered  as  the  first  of  a  series  of  eleven  waves,  of  a  mean  period  of  68  minutes,  or, 
taking  every  alternate  wave,  2  hrs.  10  mins.,  which  again  is  not  very  different  from 
Batavia« 


Times 

h.      m.          u.     m.          h.      m.          n.      in.          h.      m.          h.      in. 

14  40      16  05      16  48       17  50      18  52       19  43 

Intervals  .  • 

in.                   xn.                  xn.                   m.                   m.                  m. 

85            43            62            62            51             67 

Times 

20  50      21  50      23  09      24  00         1  32        3  10 

Intervals  .. 

60             79             51             92            98 

The  double  intervals  are — 

128     124     118     139     143  minutes. 

The  distance  is  1,805  miles  between  the  1,000  fathom  depth  off  the  Sunda 
Strait  and  150  fathoms  off  Negapatam,  the  known  soundings  not  extending  to  deeper 
water.  This,  taking  the  14  hrs.  40  mins.  wave,  gives  a  velocity  of  357  miles  an  hour, 
which  corresponds  to  a  mean  depth  of  1,880  fathoms. 

Arselar  River ^  Karihah 

At  this  port,  10  miles  north  of  Negapatam,  there  is  no  self-registering  tide  gauge, 
but  the  attention  of  the  Port  Officer  was  called  to  the  movement  of  the  water. 

He  reports  that  at  2  o'clock  in  the  morning  of  the  27th,  a  small  disturbance  was 
visible  in  the  river,  which  continued  all  the  morning.  After  1 1  o'clock  the  waves 
succeeded  one  another  with  greater  rapidity,  and  with  gradually  increasing  height. 
Between  13  hours  and  15  hours  they  were  of  about  22  inches  range,  with  a  mean 
interval  of  about  45  minutes.  From  4  o'clock  they  began  to  diminish,  disappearing 
entirely  by  11  hours  of  the  28  th. 

The  maximum  height  here  corresponds  with  the  record  of  the  diagram  at 
Negapatam,  though  the  mean  interval  mentioned  is  less,  45  minutes  instead  of  68. 
This  is  the  '  only  case  on  the  coast  of  India,  in  which  eye  observations  can  be 
compared  with  a  diagram  at  no  great  distance.  As  far  as  height  goes  they  agree, 
nor  does  the  interval  differ  so  much  as  do  those  of  the  waves  observed  in  Ceylon. 

The  only  waves,  therefore,  noted  here  appear  to  be  of  a  similar  character  to  those 
recorded  on  the  gauges. 

Q 


no  CAPTAIN  WHABTON   ON  THE   SEISMIC   SEA  WAVES. 

Madiras. 

This  gauge  is  situated  inside  the  artificial  port,  and  is  fitted  with  very  small 
inlet  holes  at  the  bottom  of  the  tube,  the  local  swell  being  ordinarily  great.  The 
diagram  is  in  consequence  very  smooth,  and  exhibits  quite  a  different  appearance  from 
the  majority  of  the  others.  The  disturbance  begins  abruptly  at  14  hrs-  33  mius.  on 
the  27th,  the  first  of  a  series  of  ten  waves  with  very  irregular  periods,  the  mean  of 
which  is  87  minutes.  This  is  quite  different  from  the  period  of  the  other  gauges,  and 
is  rather  incomprehensible. 


Times 

h.     m.         h.     m.         h.     m.         h.     m.          h.     m.         h.     m. 

14  33       16  27       17  48       19  33      21  00      22  20 

Intervals  . . 

m.                   n*                 in.                 m.                  in.                  in. 

114            81          105           87            80            67 

Times 

23  27        0  40        2  30        3  54        5  07 

Intervals  .. 

73          110            84            73 

The  distance  is  1,863  miles  from  the  1,000  fathom  line  off  Sunda  Strait  to  the 
100  fathom  line  off  Madras ;  and  taking  the  14  hrs.  33  mins.  wave,  the  velocity 
comes  out  338  miles  an  hour,  which  gives  a  mean  depth  of  1,700  fathoms. 

Vizagapatam. 

This  diagram  is  remarkable  for  the  large  number  of  small  oscillations  shown 
throughout.  These  are  in  all  .probability  due  to  the  construction  of  the  orifices 
admitting  the  water  to  the  tube,  which  permits  waves  of  short  period,  whether  local 
or  subsidiary  to  the  seismic  disturbance,  to  be  registered.  The  result  is  to  much 
confuse  the  record.  The  first  appearance  of  the  larger  waves  on  the  diagram  bears  a 
strong  resemblance  to  those  at  Port  Blair,  but  afterwards  they  lose  their  individuality 
and  it  is  difficult  to  recognise  them.  The  first  large  wave  of  6  inches  in  height  is  at 
15  hrs.  14  min.,  and  eight  other  waves  may  be  selected  with  a  mean  period  of 
77  minutes,  or  a  period  for  the  double  waves  of  2  hrs.  34  mins. 

h.    m.        h.    m.         h.    m.         h.    m.        h.    m.         h.    in.        h.    m.         li.    m.         h.    m. 

Times..   15  14  16  33  17  33  19  03  20  28  2145  22  55   0  10   130 

m.  in.  m.  m.  m.  m.  m.  m. 

Intervals  79  60  90  85  77  70  75  80 

The  double  intervals  are — 

h.    in.  h.    m.         h.    m.         h.    m. 

2  19       2  55       2  27       2  35 

It  is  useless  to  try  to  follow  the  waves  further,  though  the  disturbance  lasts  to 
21  hours  on  the  28th,  or  for  30  hours.  The  15  hrs.  14  mins.  wave  gives  a  velocity  ot 
338  miles  an  hour  for  the  distance  of  1,909  miles,  measured  from  the  1,000  fiithom 
line  off  Sunda  Strait  to  the  100  fathom  line  off  Vizagapatam. 


CAPTAIN  WHABTON   ON  THE   SEISMIC  SEA  WAVES.  Ill 

False  Point. 

This  gauge  is  situated  in  shallow  water  on  the  inshore  side  of  a  long  sandy  spit, 
which  projects  parallel  to  the  main  line  of  coast,  and  the  wave  has  to  travel  over  a 
long  distance  in  shallow  water  before  it  reaches  the  gauge.  The  outermost  sounding 
is  23  fathoms,  and  the  bank  probably  extends  much  further  to  seaward. 

The  diagram  is  remarkably  free  from  short  waves  of  all  kinds,  and  the  only 
ones  r^pstered  are  those  of  a  mean  period  of  2  hrs.  42  mins.,  of  which  six  can  be 
traced. 

k.     m.  h.     m.  h.      m.  h.    rxu  h.    in.  h.    m. 

Times       ..      16  36      19  30      22  15        1  05        3  20        6  05 

h.    in.  n.    m.  h.    m.  li.    m.  lu    m. 

Intervals  ..  2  54         2  45        2  50        2  15        2  45 

The  height  of  the  largest  wave,  the  second,  is  14  inches,  which  much  exceeds 
that  at  any  of  the  other  Indian  stations.  This  is  probably  due  to  the  long  extent 
of  very  shallow  water. 

The  16  hrs.  36  mins.  wave  gives  a  velocity  of  808  miles  an  hour  for  the  distance 
of  2,003  miles,  measured  from  the  1,000  fathom  line  off  Sunda  Strait  to  the 
23  fathoms  off  False  Point.  This  corresponds  to  a  mean  depth  of  1,400  fathoms ; 
but  if  the  extent  of  the  bank  off  False  Point  were  known,  this  mean  depth  for  the 
ocean  course  would  probably  be  indicated  as  considerably  greater. 

Ihiblat, 

This  gauge,  at  the  entrance  to  the  River  Hoogly,  is  situated  in  a  position  fairly 
open  to  the  sea,  but  the  coast  is  faced  with  wide  banks  over  which  the  waves  must 


The  diagram  is  free  from  short  undtilations,  which  much  fistcilitates  the  recogni- 
tion of  individual  large  waves. 

Twelve  waves  of  a  mean  period  of  65  minutes,  commenoing  with  a  well  marked 
one  of  8  inches  at  17  hrs.  56  mins.,  can  be  followed.  The  period  of  the  double 
waves  is  2  hrs,  7  mins.,  which  brings  us  back  to  the  Batavia  period  again. 


Times       ..     17  56      18 

in. 

50 

li.      in.          h.      m.          n.      m.          n.>      m* 

19  52      21  00      21  55      22  57 

m. 

Intervals  .  •                54 

m.                   m.                  nu                  m.                  m. 

62            68            55            62            66 

Times        ..       0  03        1 

10 

2  15        3  25        4  30     •  5  05 

Intervals  . .                67 

65            70            65            80 

double  intervals  are — 

k.    m.           h.    in. 

1  56      ,2  03 

11.    in.            n.    m.            b.    in. 

2  08        2  12  ..  2  15 
Q2 

112  CAPTAIN   WHARTON   ON   THE   SEISMIC    SEA  WAVES, 

The  distance,  measured  from  the  1,000  fathom  line  off  Sunda  Strait  to  the  150 
fathom  depth  off  Dublat,  gives  a  velocity  of  851  miles  an  hour,  which  corresponds  to 
a  mean  depth  of  1,820  fathoms. 

Dtamand  Harbour. 

This  gauge  is  situated  in  the  Eiver  Hoogly,  40  miles  from  Dublat. 

Only  one  wave  is  marked  on  the  diagram,  which  arrived  at  20  hrs.  6  mins. 

It  took,  therefore,  2  hrs.  10  mins.  to  travel  this  distance,  which  agrees  exactly 
with  the  time  taken  by  the  tide  wave,  the  disturbance  in  each  case  occurring  at 
the  local  high  water.  The  time  required  by  theory  to  travel  this  distance  over  the 
shallow  water  of  the  river,  which  averages  6  fathoms,  at  this  time  of  tide,  is 
2  hrs.  0  min. 

Kidderpore. 

This  place  is  close  to  Calcutta,  on  the  Hoogly,  and  is  40  miles  above  Diamond 
Harbour* 

Here  also  only  one  wave  is  recorded,  which,  like  that  at  Diamond  Harbour,  has 
travelled  at  the  same  pace  as  the  tide  wave,  and  arrives  at  high  water,  or  2  hrs. 
05  mins.  after  the  wave  at  Diamond  Harbour.  The  time  required  by  theory  is 
1  hr.  45  mins.  for  the  average  depth  of  8  fathoms,  but  the  channel  is  narrow  and 
tortuous,  and  the  depths  vary  from  11  fathoms  to  3  fathoms,  a  change  which  would 
doubtless  tend  to  impede  the  wave.     The  wave  was  3  inches  high. 

Beypore. 

This  gauge  is  situated  on  the  west  coast  of  Hindustan.  The  diagram  is  very 
tree  from  waves  of  short  period. 

An  irregular  small  oscillation,  but  of  longer  periods  than  at  Negapatam,  to  which 
this  diagram  bears  a  resemblance,  is  shown  from  the  beginning  of  the  diagram  at 

0  hour  of  the  27th  to  15  hrs.  57  mins.,  when  a  large  wave  of  8  inches  suddenly 
makes  its  appearance.  This  is  the  first  of  a  long  series  that  can  be  followed  for 
nineteen  waves.     These  have  a  ^eaoi  period  of  58  minutes,  or,  for  the  double  waves, 

1  hr.  56  mins, 

h,     m.         h.     m.         li.     in.         h.     m.         h,      m.         K.     m.         h.     m. 

Times        ..      15  57      17  00      17  40      18  40      19  48       20  35      21  35 
Intervals  . . 

Times        . .      22  32      23  26        0  25        1  30        2  20        3  05        4  20 
Intervals  . .  53  60  65  50  45  75  75 


m. 

m. 

pi. 

I?- 

m. 

.»»• 

m. 

63 

40 

60 

68 

47 

.60 

57 

CAPTAIN  WHARTON   ON  THE  SEISMIC  SEA  WAVES.  113 


h.    m..           h»    m 

Times        ..        5  35        6  35 

h. 

7 

m,            h.    m.            h.    m. 

30        8  25        9  20 

in.                  m. 

iDtervaJs*.                  60            55 

m.                  m. 

55             55 

The  douHe  intervals  are — 

^   103         128         107         110 

125         95         150 

115 

110  mills. 

The  distance,  measured  from  the  1,000  fathom  line  off  the  Strait  of  Sunda, 
to  the  1,000  fathom  line  off  Beypore,  is  2,090  miles;  and  the  15  hrs.  57  mins. 
wave  gives  a  velocity  of  326  miles  an  hour,  corresponding  to  a  depth  of  1,600 
fathoms.  The  largest  wave  is  at  5  hrs.  35  mins.,  or  13^  hours  after  the  first 
one,  and  is  16  inches  higlu  The  track  of  the  wave  is  unfettered,  but  it  has  to  turn 
Cape  Comorin. 

Bombay. 

This  gauge  is  situated  on  the  inner  side  of  the  peninsula  forming  the  harbour, 
which  is,  however,  open  to  the  south,  whence  the  wave  would  come. 

The  wave,  after  passing  Beypore,  would  travel  inside  the  Laccadive  Group,  where 
the  depths  are — as  far  as  they  are  known — suflSicient  to  permit  it  by  this  route  to  out- 
strip the  undulation  which  would  pass  through  the  Nine  Degree  Channel  and  then 
turn  to  the  north ;  a  longer  course,  but  in  deeper  water. 

On  approaching  Bombay  the  wave  must  pass  over  a  good  deal  of  shallow  water. 
The  diagram  shows  one  crest  only  of  any  magnitude,  at  18  hrs*  50  mins.  This  is  at 
high  water,  and  a  very  small  disturbance  is  recorded  at  the  succeeding  low  and  high 
water.  The  distance  from  the  1,000  fathom  line  off  Sunda  Strait  to  the  probable 
position  of  the  1,000  fathom  line  off  Bombay  is  2,483  miles ;  and  the  velocity  is 
336  miles  an  hour,  corresponding  to  a  depth  of  about  1,700  fathoms.  The  height  of 
the  wave  may  be  taken  as  6  inches. 

It  is  very  remarkable  that  the  disturbance  should  b?  confined  to  this  single  wave, 
but  the  run  of  the  tidal  streams  is  very  strong  in  Bombay  Harbour. 

Karachi. 

Here  the  tide  gauge  Is  in  the  narrow  estuary  forming  the  harbour.  A  very 
small  oscillation  appears  at  5  hrs.  30  mins.  on  the  27th,  which  is  continuous  until  the 
first  great  wave  at  18  hrs.  40  mins.  This  wave  is  preceded  by  a  well  marked 
negative  tvave,  but  the  crest  preceding  is  not  in  accordance  with  the  subsequent 
period,  and  is  too  small  to  be  taken  as  the  wave  corresponding  to  those  selected  in 
the  other  Indian  Diagrams.  The  18  hrs.  40  mins.  is  the  first  of  a  series  of  sixteen 
waves,  and  is  12  inches  high.  The  mean  period,  omitting  the  laat  wave,  is  69  mins., 
and  for  the  double  waves  2  hrs.  18  mins. 


114  CAPTAIN  WHARTON  ON  THE   SEISMIC   SEA  WAVES. 


h.    nu        h.     in.        h. 

m.        h. 

m.        h. 

m. 

h. 

ra.          h. 

m. 

Times 

18  40     19  56     20 

50     21 

55     23 

10 

0 

35       1 

50 

Intervals 

m.                 m. 

76           54 

m. 

65 

in. 

75 

m. 

85 

m. 

75 

m. 

70 

Times 

3  00       4  15       5 

15       6 

30       7  30 

8 

30      S 

40 

Intervals 

75           60 

75 

60 

60 

70 

70 

Times 

10  50     12  30 

Intervals 

100 

The  double 

intervals  are — 

h.    m.         h.    m. 

2  10       2  20 

2  40 

2  25 

h.    m. 

2  15 

h.    m. 

2  00 

h.    m. 

2  20 

The  distance,  measured  from  the  1,000  &thom  line  oif  Sunda  Strait  to  tho 
probable  position  of  the  1,000  fathom  line  off  Karachi,  piMSsing  through  the  Nine 
Degree  Channel,  and  to  the  northward  outside  the  Laccadive  Islands,  is  3,032  nules, 
for  which  the  18  hrs.  40  mins.  wave  gives  a  velocity  of  340  mil^  an  hour.  This 
corresponds  to  a  mean  depth  of  1,710  fathopos;  whereas  th@  probable  depth  &om, 
existing  soundings  is  2,150  fathoms.  In  several  parts  of  the  route,  however>  the 
chart  is  a  blank,  and  notably  in  the  Nine  Degree  Channel. 

The  disturbance  lasts  u^til  the  end  of  the  diagram,  or  till  %2  hours  of  the  28th. 

Aden. 

The  tide  gauge  is  p,t  Steamer  Point,  th^^t  is,  in  the  bay  behind  the  peninsula  of 
Aden,  protected  from  the  advancing  i^ave,  which  would  hav^  to  change  its  course 
ISO^  to  reach  the  gauge. 

The  wave  would  travel  over  9  jniles  of  shallow  Wftter  in  so  doii^g,  The  diagram 
is  free  from  waves  of  jshort  period. 

The  disturbance  is  inappreciable  until  13  hours  on  the  STth,  whan  a  small  wave 
<>f  2  inches  appears-  After  two  others,  a  decided  wave  of  5  inches  ia  recorded  at 
17  hrs,  50  mm»,    ' 

This  is  the  first  of  seventeen  waves  at  fairly  equal  intervals,  which  can  be 
followed  with  a  mean  period  of  67  minutes  ;  or  for  the  double  waves  2  hrs.  14  mins, 

h.      m.        h.      m.        h.      m.        h.      m.         h.      in.        h.     m.        h.      m.         h.      m. 

TinoBs   ..  17  50  18  50  19  50  20  50  22  10  23  10  23  55   1  05 

ID.  ID.  ID-.  in.  n.  m.  in.  in. 

Intervals,.  60  60    .       60  SO  60  45  70  70 

Times      ..      2  15     3     25       jS  00       6  00       7  18       8  10       9  00     10  15     11  45 
Intervals..  70  9§  €0  78  52  50  75  90 

^he  double  intervals  are — 

Km.         h.     m.       ^.    m.         h.    m.         h.    m.  1*.    m.         b.    m.         h.    n. 

2  00       2     0       1   45        2  20       2  45       2  18       1   42       2  45 


CAPTAIN  WHARTON   ON   THE   SEISMIC   SEA   WAVES.  115 

The  distance,  measured  from  the  1,000  fathom  line  off  Sunda  Strait,  through 
the  Nine  Degree  Channel  and  north  of  Sokotra,  to  the  1,000  fathom  line  off  Aden,  is 
3,642  miles. 

The  17  hrs.  50  mins.  wave  gives  a  velocity  of  347  miles  an  hour,  corresponding 
to  a  mean  depth  of  1,770  fathoma  The  prohable  mean  depth  from  known  soundings 
is  2,100  fathoms. 


CEYLON. 


Eye  Observations. 

The  report  of  the  Surveyor-General  of  Ceylon,  reproduced  on  pp.  116  to  124,  is 
interesting  in  many  details.  Unfortunately  it  does  not  furnish  any  precise  data  on 
the  points  of  time  and  height  of  the  wave.  In  one  respect,  however,  it  is  very 
worthy*  of  consideration. 

At  all  the  places  where  the  disturbance  was  remarked,  the  observers  agree  that 
the  period  of  the  wave  was  comparatively  short.  From  5  to  20  minutes  are  named 
as  elapsing  between  successive  crests.  Nov^  this  is  quite  different  from  all  the 
diagrams  from  gauges — which  show  only  long  waves ;  and  it  is  much  to  be  regretted 
that  no  gauge  by  which  comparison  might  have  been  made  between  eye  observation 
and  mechanical  record  was  at  work  at  any  of  these  places. 

At  no  Indian  tidal  station  are  any  short  waves  shown,  of  any  height  greater 
than  3 or  4  inches;  and  at  Negapatam,  which  is  only  100  miles  further  off,  and 
which,  except  for  being  inside  a  bar,  is  equally  favourably  situated  for  receiving  the 
waves — only  one  period  of  under  an  hour,  viz.,  43  minutes,  is  recorded. 

Eye  observationa  of  this  description  are  very  liable  to  error,  especially  in  point 
of  height ;  but  when  many  independant  observers  at  different  places  agree  fairly, 
the  evidence  is  much  strengthened. 

The  range  at  Galle  is  estimated  at  fi  feet,  at  Colombo  7\  feet,  at  Valluwedditherai 
4  feet,  at  Trincomalee  8  feet,  Batticaloa  8  feet,  Arugam  4  feet,  Hambantota  12  feet. 

These  short  waves  must  probably  be  regarded  as  super-seismic  waves ;  that  is, 
waves  of  short  period,  but  of  greater  height,  imposed  on  the  longer  wave  that  alone 
affected  the  gauges.  Their  duration  was  brief  compared  with  that  of  the  long  waves 
recorded  on  the  diagrams. 

There  does  not  seem  to  be  any  difficulty  in  assuming  that  these  waves  were  in 
their  origin  synchronous  with  the  longer  imdulations,  and  their  speed  of  translation 
would  be  about  the  same.  It  is,  therefore,  not  surprising  to  Hnd  the  time  of  their 
arrival  agreeing  very  well  with  that  of  the  longep  waves,  as  far  as  the  incomplete 
information  admits  of  comparison. 


US  CAPTAIN   WHARTON   ON   THE    SEISMIC    SEA  WAVES. 

At  Batticaloa,  however,  the  first  wave  of  24  inches  was  noted  at  7  hours  on  the 
27th.  This  is  1  hr.  28  mins.  Greenwich  time,  or  one  hour  and  a  half  before  the 
great  wave  left  Krakatoa.  It  must,  therefore,  have  been  due  to  one  of  the  earlier 
waves* 

Assuming  that  it  travelled  at  a  speed  of  about  350  miles  an  hour,  this  wave 
must  have  left  the  Strait  of  Sunda  at  about  3.40  a.m.  There  is,  however,  no  large 
wave  recorded  in  the  Strait  at  or  about  this  time,  none  being  noted  as  reaching  the 
shores  between  1.30  and  6. 

To  what  this  early  disturbance  at  Batticaloa  was  due  is  therefore  a  mystery. 
The  largest  wave  is,  however,  stated  to  have  occurred  at  about  noon,  which  agrees 
with  the  Galle  observations. 


2%6  Surveyor-GeneraVs  Report  on  Tidal  Waves  on  the  Coast  of  Ceylon^  resulting  fronk 
the  Eruptions  in  the  Strait  of  Sunda  on  the  26th  and  27th  August,  1883. 

Subveyoe-General's  Office,  Colombo, 
10th  April,  1884. 

Sm, 

With  reference  to  your  notice  of  February  12th  in  'Nature'  of  February  14th, 
page  355,  I  have  the  honour  to  report  to  you  the  result  of  my  inquiries  regarding  the 
effects,  as  observed  in  Ceylon,  of  the  eruptions  at  Krakatoa,  in  the  Strait  of  Sunda,  on 
the  26th  and  27th  of  August  last.  The  various  stations  from  which  I  have  received 
reports  are  marked  on  the  accompanying  map. 

The  questions  asked  were  : — 

(a.)  The  extreme  rise  and  fall  of  tide,  and  the  number  of  times  the  wave 

appeared  to  come  and  go  ? 
(6.)  Whether  noises  were  heard  or  any  motion  of  the  earth  felt  ? 
(c.)   The  exact  time  as  near  as  obtainable  ? 
(d.)  Whether  any  crack  or  fissure  had  been  observed  inland  or  along  the 

coast  ? 

Galle. — The  Master  Attendant  reports  that  four  unusual  waves  were  noticed  in 
the  port  at  the  hours  of  one,  two,  three,  and  half-past  four  on  the  afternoon  of  August 
the  27th,  the  last  of  which  he  witnessed  hhnself,  and  recorded  as  follows : — "  A 
very  unusual  receding  of  the  sea,  the  small  boats  at  their  usual  anchorage  being  left 
by  it — a  thing  I  had  never  seen  before  during  my  tenure  of  office,  since  1860. 

"  It  was  about  1^  minutes  in  recession,  and  then  about  the  same  time  in  a  sort 
of  suspensory  standstill,  when  it  commenced  quietly  to  rise  again,  taking  about  the 


CAPTAIK   WHARTON   ON   THE    SEISMIC   SEA  WAVES. 


117 


same  1^  minutes  to  reach  the  level  of  our  highest  high  water-marks,  thus  making, 
from  the  lowest  mark  of  recession  to  it,  a  diflference  of  8  feet  10  inches. 

*'  The  usual  tide  rise  and  fall  here  is  about  2  feet,  and  so  the  great  difiference 
caused  by  this  disturbance  was  palpably  from  unusual  recession/' 

Colombo. — The  Master  Attendant  reports  : — "  I  find  it  diflficult  to  get  at  the 
exact  hour  of  the  commencement  of  the  tidal,  disturbance  in  this  harbour,  but  I  am 
informed  by  the  man  in  charge  of  the  landing  jetty  that  about  2.30  p.m.  on  the  27th 
of  August  there  was  a  suddeto  rise  of  the  sea  to  about  15  inches  above  the  highest 
spring  tide,  and  that  shortly  afterwards,  within  15  minutes,  the  sea  fell  to  about 
3  feet  below  the  lowest  spring  tide.  I  witnessed  between  3.30  and  4.30  p.m.  four 
rises  and  falls  of  the  sea,  and,  as  near  as  I  can  judge,  there  were  7  feet  6  inches 
between  the  highest  point  to  which  the  sea  rose  and  the  lowest  point  to  which  it  fell. 

Fig.  12. 


During  this  time  there  was  a  strong  cun*ent  in  the  harbour,  which  carried  away  the 
stern  moorings  of  some  of  the  steamers  in  port,  and  swung  them  roimd  against  the 
wind.  The  tidal  disturbance  went  on  more  or  less  till  8  p.m.  of  the  27th,  and  I 
observed  it  again  the  next  day  about  midday,  but  the  rise  and  fall  of  the  tide  then 
did  not  exceed  1  foot." 

Negomho. — The  information  from  this  station  is  very  meagre.  The  Mudaliyar 
of  Alutkuru  Korale  North  reported  to  the  Assistant  Government  Agent : — "  No 
changes  in  the  sea  or  land  occurred  on  the  day  in  question. 

R 


118  CAPTAIN  WHABTON  ON  THE   SEISMIC  SEA  WAVES. 

^'  I  am  informed  that  there  had  been  an  unusual  ebb  tide  and  flood  tide  twice 
within  half-an-hour  in  the  mouth  of  the  lake." 

I  have  had  no  reports  from  Chilaw  or  Puttalam,  but  Mr.  ViGOBS,  the  Police 
Magistrate  of  Kalpitiya  (Calpentyn),  sent  me  an  interesting  and  quaint  report  from 
Mr.  Vansanden,  the  Preventive  Officer  at  Dutch  Bay,  which  I  give  verbatim,  as  in 
one  paragraph,  where  he  describes  the  wash-away  of  a  belt  of  land  about  2  or  3  chains 
in  extent,  including  the  burial  ground,  it  appears  as  if  the  dead  had  sought  shelter 
with  the  living  in  a  neighbouiring  cocoa-nut  garden  I 

"  The  so-called  tidal  wave  had  been  felt  here,  too,  on  the  27th  ultimo,  about 
3  o'clock  p.m.  The  tide  is  said  to  have  been  observed  coming  in  and  going  out  three 
or  four  times  in  the  space  of  one  hour  ;  this  had  been  witnessed  by  the  fishers  who  had 
been  out  at  sea.  The  rise  of  the  tide  was  so  much  above  the  usual  water-mark  that 
many  of  the  low  morasses  lying  in  close  proximity  to  the  seaside  were  replete  with 
water  that  flowed  into  them.  However,  the  water  thus  accumulated  did  not  remain 
long,  but,  forming  into  a  stream,  wended  its  course  in  a  southerly  direction,  through 
low  lands,  to  a  distance  of  nearly  a  quarter  of  a  mile,  and  found  a  passage  back  to 
the  sea  ;  thus  the  water  that  had  so  abruptly  covered  up  such  an  extent  of  land  did 
not  take  many  days  in  draining  off. 

"  Eke,  I  must  say  that  the  receding  waters  were  not  slow  behind  in  their  action, 
for  they  washed  away  a  belt  of  land  about  2  or  3  chains  in  extent,  including  the 
burial  ground  situated  on  the  coast  to  the  south-west  of  the  bay,  designated  as  the 
Parava's  or  Fisher's  Quarters,  compelling  the  inhabitants  to  seek  shelter  in  a  neigh- 
bouring cocoa-nut  garden. 

'*  On  the  above  date  noises  were  heard  by  several  persons,  resembling  the  rumb- 
ling of  distant  thunder,  or  rather  that  of  the  booming  of  cannon,  which  lasted  frt)m 
7  to  10  a.m. 

"  No  motion  of  the  earth  was  felt,  nor  have  I  heard  of  any  crack  or  fissure 
having  occuired  either  inland  or  along  the  coast  in  the  vicinity." 

Manndr. — The  reports  from  this  station  are  conflicting,  and  it  is  very  doubtftd 
whether  any  sudden  rise  or  fall  of  the  sea  was  actually  witnessed  there  by  anyone. 
Mr.  Fowler,  the  Assistant  Government  Agent,  reported : — "  I  have  caused  carefril 
inquiry  to  be  made  on  the  subject,  but  find  that  no  rise  or  fall  of  the  sea  was  noticed 
here  on  the  27th  ultimo,  although  loud  sounds,  resembling  the  report  of  distant  cannon, 
were  heard  to  the  eastward  on  that  date. 

"  I  may  mention  that  there  has  been  a  curious  change  in  the  colour  of  the  sun's 
disc  noticed  in  the  early  morning  and  in  the  evening  since  the  9th  instant  [Septem- 
ber, 1883].     It  has  appeared  to  be  of  a  bluish-green  colour.*' 

In  reporting  on  the  state  of  the  Searchers'  House  at  the  South  Bar,  the  Sub- 
Collector  of  Mannllr  wrete  on  September  the  17th  to  the  Collector  of  Customs  at 
Jaifiia  as  follows  : — **  I  went  to  see  the  house  on  Saturday  afternoon,  and  found  it 
to  be  very  much  damaged,  the  sea  having  washed  away  a  great  part  of  the  sand 


CAPTAIN  WHARTON  ON  THE  SEISMIC  SEA  WAVES.  119 

put  for  the  floor  of  the  building,  although  the  building  is  at  a  distance  of  about 
255  feet  from  the  sea.  The  sea  appears  to  have  risen  all  of  a  sudden,  during  the 
latter  part  of  last  month/' 

In  forwarding  a  copy  of  this  report,  Mr.  Twynam,  the  Government  Agent,  says : 
— ^*  It  appears  that  there  must  have  been  something  unusual  in  the  tide  off  the  southern 
coast  of  Manner  in  August  f  but  he  adds : — "  I  was  told  by  the  gentlemen  who  came 
up  in  the  '  Serendib '  with  Mr.  Justice  Clarence  that  they  were  informed  that  nothing 
was  observed  at  Paumben." 

It  may  be  inferred  from  this  that  the  strength  of  the  tidal  wave  had  become 
very  much  modified  or  exhausted  by  the  time  it  reached  the  Gulf  of  Mann&r ;  and 
from  a  further  report  of  the  Assistant  Government  Agent  I  am  inclined  to  the  belief 
that  the  damage  done  to  the  Searchers'  House  was  not  caused  by  the  tidal  wave. 
Mr.  Twynam  goes  on  to  say  : — "  Nothing  unusual  was  noticed  in  Jaffna  or  at  Kaits 
in  regard  to  the  tide.  No  one  seems  to  have  heard  any  peculiar  noises  in  Jaffna,  or 
to  have  felt  any  motion  of  the  eartL 

"  I  have  not  yet  received  any  information  of  any  crack  or  fissures  having  been 
observed  anywhere  on  the  coast/' 

Mr.  Twynam  has  furnished  me  with  reports  also  from  the  Sub-Collectors  of 
Elankesanturai,  Valluwedditherai  and  Point  Pedro,  on  the  most  northerly  part  of 
Ceylon  on  the  Bay  of  Bengal  exposed  to  the  north-west  roll  or  wave  from  the  Strait 
of  Sunda,  from  which  I  quote  as  follows  : — 

Kcmkesanturai. — "  The  extreme  rise  and  fall  of  the  tide,  though  not  noted,  was 
about  2  to  3  feet ;  and  the  number  of  times  the  tide  appeared  to  come  and  go,  though 
not  counted  over  at  the  time,  would  be  about  3  or  4  times.  No  noises  were  heard, 
nor  was  any  motion  of  the  earth  felt  on  the  occasion.  Though  the  exact  time  cannot 
be  stated,  it  was  first  noticed  about  midday,  when  a  boat  with  import  cargo  at  the 
wharf  was  said  to  have  got  aground  all  of  a  sudden.^' 

Valluwedditherai. — "  The  usual  rise  and  fall  of  the  tide  at  this  time  of  the  year 
is  from  2^  to  3  feet ;  on  the  27th  ultimo  the  rise  was,  at  its  maximum,  2  feet  more 
than  ordinary ;  the  highest  rise  was  at  about  2.30  p.m  The  number  of  times  the 
waves  appeared  to  advance  and  recede  was  about  10  or  12. 

''A  man  of  this  place  informed  me  that  he  counted  16  times  from  12  to  3  p.m., 
in  which  the  wave  appeared  to  come  and  go. 

"  No  noises  were  heard,  nor  was  any  perceptible  motion  of  the  earth  felt. 

^*  The  exact  time  was  not  noted,  but  it  was  about  a  quarter  past  12  p.m.  that  the 
rise  in  the  tide  was  observed. 

"  No  cracks  or  fissures  have  been  observed  either  inland  or  along  the  coast." 

Point  Pedro. — August  the  29th,  1883. — "A  strange  phenomenon,  such  as  had 

never  been  witnessed  before  by  the  oldest  masters  of  vessels  and  others  belonging  to 

this  place,  was  observed  in  the  sea  on  Monday  last,  the  27th  instant,  commencing  in 

the  forenoon  and  ending  about  sunset.     The  tide  rose  and  fell  in  rapid  succession 

B  2 


120  OAPTAm   WHARTON  ON   THE  SEISMIC   SEA  WAVES. 

more  than  a  dozen  times  ;  and  one  or  two  boats  with  cargo  which  were  floating  were 
suddenly  foimd  to  be  high  and  dry.  The  wind  at  the  time  was  blowing  half  a  gale 
fi-om  south-west."  And  Mr.  Maartensz,  Sub-Collector,  on  September  the  19th,  wrote 
again  : — ''I  have  the  honor  in  continuation  of  my  report  (August  the  29th,  1883)  to 
inform  you  that  from  about  the  forenoon  till  sunset  of  the  27th  ultimo,  the  rise  and  fall 
of  the  sea  was  observed  by  me  and  the  people  in  the  wharf  to  have  been  (imlike  the 
usual  rise  and  fall  of  the  tides)  of  very  frequent  occurrence.  The  rush  of  water,  both 
when  the  sea  rose  and  when  it  fell,  was  with  some  force,  giving  it  a  hissing  sound ; 
but  only  once,  and  that  was  between  3  and  4  in  the  afternoon,  the  sea  rose  and  flowed 
in  beyond  the  ordinary  limit  and  went  down  rapidly  in  a  few  minutes,  so  low  as  to 
cause  a  boat,  which  had  put  off  with  a  cargo,  to  get  aground  high  and  dry,  and  another 
empty  boat  to  capsize  at  the  wharf.  The  extreme  rise  and  fall  of  water  was  not  noted 
at  the  time,  but  it  must  have  been  about  2  feet  above  the  ordinary  level  at  the 
tides ;  and  the  rise  and  fall  of  the  sea  must  have  been  over  twenty  times.  The 
wind  at  the  tijne  of  the  occurrence  was  blowing  rather  stiff  from  south-west,  and 
I  could  see,  with  the  aid  of  a  glass,  that  the  vessels  in  the  harbour  were  tossed 
about  in  different  directions,  and  the  sea  about  their  anchorage  was  rising  in 
bubbles. 

"  No  noises  were  heard,  nor  was  any  motion  of  the  earth  felt  here  or  in  the 
neighbourhood.'' 

MuUaittivu. — Mr.  Samuel  Haughton,  Assistant  Government  Agent, in  forwarding 
some  interesting  reports  by  several  of  his  headmen,  says  : — "  There  can  be  no  doubt 
as  to  the  phenomena,  reported  by  the  headmen  along  the  coast,  having  been  connected 
with  the  recent  fatal  volcanic  disturbance  in  the  Strait  of  Sunda ;  Mr.  Parker's  report 
from  Hambantota  as  to  the  occurrence  of  the  phenomena  so  far  south,  shows  that 
they  must  have  been  experienced  along  the  whole  eastern  coast  of  Ceylon. 

"  The  reports  of  the  sea -coast  Vidahus  of  MuUaittivu  and  Kokkulai  are  of  special 
interest  as  showing  that  at  sunrise  on  August  the  27th  the  sky  to  the  east  was 
murky,  and  the  rays  of  the  rising  sim  obscured  by  the  smoke  in  the  Strait  of  Sunda. 

**  The  subsidence  and  return  of  the  sea  was  noticed  all  along  the  coast.'' 

The  Police  Vidahu,  of  MuUaittivu,  gives  the  foUowing  particulars  : — "  The  sea 
receded  to  16  fathoms  distance,  and  came  back  to  the  shore,  I  am  told.  This  took 
place  only  once. 

"  No  one  heard  any  noise  here. 

"  No  one  saw  any  cracks  in  any  vUlages  or  in  the  jimgle. 

*'  It  did  not  appear  that  the  earth  shook  here. 

"  The  sun  was  not  bright  in  the  morning  at  about  6  o'clock,  and  in  the  evening 
from  4  o'clock  its  rays  were  green." 

Similar  reports  were  sent  in  by  the  Police  Vidahus  of  Chemmalai  and  Kokkulai, 
in  which  it  is  stated  that  the  sea  receded  and  rose  again — ^that  sounds  as  of  firing  of 
cannon  at  Trincomalee  were  heard,  and  the  Yidahu  of  Kokkulai  states  that  from 


CAPTAIN  WHARTON  ON  THE  SEISMIC   SEA  WAVES.  121 

August  the  27th  to  September  the  4th  the  sun  and  moon  were  blue-coloured.  No 
cracks  or  fissures  were  observed  in  the  ground,  and  it  did  not  shake. 

TrincoTnalee. — The  Chief  Clerk  of  the  Royal  Engineers  Department  at  this 
station  furnishes  a  report,  from  trustworthy  information  supplied  by  the  head  mason 
who  was  building  a  sea-wall  at  Fort  Frederick,  from  which  I  quote : — 

"  The  extreme  rise  (of  tide)  4  feet  at  an  average. 
»>  lall  ,}  9) 

The  number  of  times  the  wave  appeared  to  come  and  go  was  about  thirteen  times, 
of  which  the  sixth,  seventh  and  eighth  were  those  that  caused  more  or  less  the 
extreme  rise  and  fall  above  stated,  and  the  rest  were,  of  course,  of  a  kind  not  to 
attract  so  much  the  notice  of  the  working  men,  bearing  simply  the  appearance  of  a 
little  extraordinary  ebb  and  flow  of  the  sea-water.  No  noise  heard  (except  what 
would  be  heard  when  a  heavy  swell  of  the  sea  would  all  of  a  sudden  overflow  its 
shore),  nor  any  motion  of  the  earth  felt, 

"The  exact  time  was  1.30  p.m.  on  Monday,  August  the  27th,  1883. 

"  The  sea  receded  three  times  and  retiuned  with  force  in  a  manner  that  would 
attract  anyone's  notice  on  the  spot ;  and  the  ground  from  the  shore  to  a  distance  of 
about  30  feet,  no  sooner  appeared  bare  and  displayed  its  sediments  with  fishes 
struggling  about,  and  a  few  men  (fishers)  attempted  to  try  their  luck,  than  the  sea 
returned.     In  about  5  minutes  the  sea  on  that  day  receded  and  returned  twice. 

"  A  similar  change  I  remember  took  place  at  Gun  Wharf  Pier,  when  work  was 
going  on  there,  with  a  slight  shock  of  an  earthquake,  on  December  the  31st,  1881, 
at  8  o'clock  am.*' 

Batticaloa. — In  forwarding  reports  by  the  Sub-Collegtor  and  Signaller  at  that 
station,  Mr.  Elliott,  Acting  Government  Agent,  remarks  : — "  I  was  myself  absent  from 
Batticaloa  on  that  day,  and  observed  nothing,  but  on  the  27th  ultimo,  at  Eoklmunai, 
Mr.  Chbistie,  of  the  Public  Works  Department,  told  me  he  had  heard  loud  explosions 
seawards  that  morning,  and  that  as  they  sounded  like  the  discharge  of  heavy  artillery 
he  presumed  some  man-of-war  was  practising  with  her  big  guns  out  of  sight  of  land^ 
as  he  could  see  no  ships. 

^'  Captain  Walkeb  and  Mr.  Fielder,  at  Tumpalancholai  and  Mah&  Oya,  on  the 
Badulla  road,  at  various  times  on  the  forenoon  of  the  27th,  were  puzzled  by  hearing 
noises  as  if  blasting  was  going  on,  though  there  was  nothing  of  the  sort  for  a  very 
considerable  distance,  if  anywhere,  in  this  district. 

**  Mr.  Smith,  of  the  Public  Works  Department,  observed  the  wave  which  came 
up  the  lake,  and  rose  at  his  jetty  about  2  feet. 

"  I  have  not  had  any  intimation  of  any  fissure  or  crack  or  any  motion  of  the 
earth  in  this  district." 

The  Sub-Collector  states  that  about  6  p.m.  on  the  evening  of  the  26th  he  heard 


122  CAPTAIN  WHARTON  ON   THE  SEISMIC   SEA  WAVES. 

"  a  loud  report  as  if  a  cannon  was  discharged  down  southward,"  which  he  and  the 
people  near  him  thought  to  be  thunder ;  then,  on  the  morning  of  the  27th,  about 

7  a.m.,  he  saw  the  water  receding  rapidly,  and  it  rose  quite  suddenly  a  few  minutes 
afterwards  to  about  2  feet  over  ordinary  tide,  which  caused  him  to  remark  to  the 
people  that  what  was  going  on  was  "  the  effect  of  an  earthquake  somewhere,"  as  a 
similar  phenomenon  occurred  here  on  December  the  31st,  1881,  immediately  after  the 
shock  of  earthquake  had  been  felt. 

"  The  rise  and  fall  of  water  continued  the  whole  of  Monday  at  intervals  of  about 
10  minutes,  the  extreme  rise  and  fall  being  about  2  feet  each  time ;  at  about  3  p.m. 
on  Monday  I  heard  the  noise  of  water  rushing  in  with  some  force,  and  on  peeping 
through  the  window  I  observed  the  water  coming  foaming  near  the  causeway,  and 
this  time  the  water  rose  fully  3  feet ;  the  rise  and  fall  continued  on  Monday  night  too, 
and  was  slightly  perceptible  till  about  10  a.m,  on  Tuesday. 

"At  the  Bar  the  rushing  of  water  in  and  out  caused  several  openings  in  the  sand- 
bank, washing  away  a  small  portion  of  *  Bones'  Island '  at  the  mouth  of  the  lake,  as 
reported.  People  on  boaixl  the  vessels  at  the  anchorage  mentioned  to  me  that  the 
vessels  were  much  shaken  about  and  positions  changed  every  quarter  or  half  hour  on 
Sunday  night." 

Mr.  Casinadeb,  the  Signaller  at  the  Flagstaff,  states  that  ^'  about  midnight  on 
Sunday,  the  26th  ultimo,  I  heard  about  five  or  six  times  a  noise  similar  to  that  of  a 
cannon  being  discharged  at  intervals  of  15  minutes,  I  believe,  towards  the  sea  in  the 
east.  Very  early  in  the  morning  I  observed  the  cargo  boats  that  were  moored  in  the 
lake  just  opposite  to  Mr.  Athebton's  bimgalow  were  on  the  move ;  but  when  I  noticed 
it  very  closely,  I  found  the  rise  and  fall  of  water  at  intervals  of  about  10  minutes ; 
and,  in  my  opinion,  the  height  of  the  wave  in  the  sea  near  the  Bar  rose  to  about 

8  feet  about  noon  on  Monday,  and  in  the  lake  it  was  about  3  feet  high ;  and  on 
Monday  morning,  too,  about  three  times  I  noticed  a  noise  similar  to  that  of  the 
discharge  of  a  cannon  in  the  sea  towards  the  east,  and  after  the  highest  rise  of  the 
water  at  noon  no  such  noise  was  heard." 

The  Acting  Gk)vemment  Agent,  Eastern  Province,  gives  further  interesting 
particulars  obtained  by  him  while  on  a  tour  in  the  southern  part  of  his  province  in 
October  last,  regarding  the  effects  of  the  tidal  wave  at  Arugam  Bay,  and  of  the  death 
of  one  Moorwoman,  whom  he  believes  to  have  been  a  *'  solitary  victim  out  of  Java  of 
the  recent  earthquake." 

Arugam  Bay  is  the  most  easterly  bay  in  which  ships  can  anchor  on  the  east  coast 
of  Ceylon.  It  is  situated  nearly  half-way  between  Batticaloa  and  Hambantota,  and 
is  directly  exposed  to  any  tidaJ  wave  from  the  direction  of  the  Strait  of  Sunda. 
From  the  information  given  by  the  Batamahatmaya  of  Panama,  the  wave  appears  to 
have  been  felt  with  greater  force  at  Arugam  Bay  than  at  any  other  place  on  the  coast 
from  which  I  have  reports. 

The  Batamahatmaya  says  : — "  On  one  day  towards  the  end  of  July  "  [this  must 


CAPTAIN  WHARTON  ON  THE  SEISMIC  SEA  WAVES.  123 

be  a  mistake  for  August]  '^  I  was  at  Panama  and  heard  of  an  accident  at  the  Bar  at 
Arugam  Bay. 

"  Three  Moorwomen,  three  children,  and  a  man  were  crossing  it  about  3  p.m.  A 
big  wave  came  up  from  the  sea  over  the  Bar  and  washed  them  inland.  Soon  after 
the  water  returned  to  the  sea.  The  man  said  that  the  water  came  up  to  his  chest :  he 
is  a  tall  man.  These  people  were  tumbling  about  in  the  water,  but  were  rescued  by 
people  in  boats  who  were  fishing  in  the  Kalapuwa  (inland  estuary).  They  lost  the 
paddy  they  were  carrying,  and  one  of  the  women  died  two  days  after  of  her 
injuries. 

"  I  was  further  informed  by  the  tindals  [masters  of  vessels]  in  the  ships  anchored 
at  the  Bay  that  they  felt  aU  of  a  sudden  their  vessels  go  downwards  \mtil  they 
plainly  saw  the  ground,  and  the  ships  were  drawn  seawards,  and  the  people  on  the 
shore  declared  the  anchors  were  exposed  to  sight.  After  this  the  wave  came  in 
and  raised  the  vessels  and  overflowed  the  Bar. 

"  Up  the  Navalaru  (a  stream  further  south)  where  the  water  was  heretofore 
sweet,  it  has  been  salt  since  that  time  to  a  distance  of  at  least  a  mile  and  a  half 
in  a  direct  line  from  the  sea.  In  Panama  similarly  the  salt  water  has  come  a  long 
way  inland." 

From  the  testimony  of  the  tindals  and  the  people  on  the  shore  at  Arugam  Bay  it 
is  quite  evident  that  the  negative  wave  or  general  fall  of  the  sea-level,  was  the  first 
to  affect  the  shores  of  Ceylon,  and  this  is  corroborated  by  the  more  accurate  and 
tnistworthy  information  obtained  by  Major  Baird,  R.E.,  from  the  various  self- 
registering  tide-gauges  under  his  charge  at  the  Indian  tidal  stations,  which  I  shall 
refer  to  hereafter. 

Harnhantota. — This  is  the  most  southerly  siation  in  Ceylon  from  which  I  have 
received  reports,  and  it  completes  the  circuit  of  the  island.  Mr.  E.  M.  D.  Byrde,  who 
was  acting  Government  Agent  at  the  time,  reported  that  on  the  afternoon  of  August 
the  27th,  "between  the  houre  of  12  and  2  o'clock,  the  sea  kept  on  rising  several 
feet  above  its  ordinary  level,  and  receding  to  a  great  distance,  leaving  the  jetty  almost 
dry,  the  water  at  the  extreme  end  of  it  not  being  more  than  knee-deep. 

"  About  every  20  minutes  the  sea  completely  covered  the  jetty,  and  rose  so  high 
that  it  washed  away  one  of  the  old  surf-boats  that  was  high  and  dry  near  the  main 
road.  I  sent  out  a  canoe  to  bring  back  the  boat,  but  the  current  was  so  strong  that 
it  was  impossible  to  save  it,  as  it  was  carried  with  great  rapidity  across  the  bay  and 
then  dashed  to  pieces  on  the  opposite  shore. 

"  The  waves  did  not,  as  is  sometimes  the  case,  break  on  shore  with  violence,  but 
the  sea  rose  gradually  and  similarly  receded,  and  I  should  say,  judging  from  an 
examination  of  the  shore  this  morning,  that  it  must  have  risen  12  feet,  or  more,  above 
its  ordinary  leveL 

"  The  fishermen  with  some  difficulty  saved  the  canoe,  and  with  the  help  of  a 
large  gang  of  prisoners  the  cargo  boat  was  saved  from  being  carried  out  to  sea. 


124 


CAPTAIN  WHARTON  ON   THE   SEISMIC   SEA  WAVES. 


''  The  oldest  inhabitants  here  never  previously  witnessed  such  an  occurrence,  and 
they  considered  it  worthy  of  notice." 

I  annex  a  list  of  the  barometrical  observations  made  on  the  26th  and  27th 
of  August  last  at — 


Mean  reading  for  the 
Month. 

Difference. 

9iA.u. 

3|P.M. 

9i  A.M. 

3^  P.M. 

9i  i..u. 

3i  P.11. 

:g  rColombo       

29-832 

29-721 

29-862 

29-768 

--020 

--037 

04 

Galle 

29-769 

29-628 

29-848 

29-728 

--074 

-•100 

^ 

Hambantota           

29-789 

29-675 

29-811 

29-712 

--022 

-•037 

Batticaloa 

29-776 

29-667 

29-800 

29-711 

-•024 

-•044 

o 

^Trinoomalee            

29-697 

29-470 

29-636 

29-637 

--039 

-•067 

•$  fColombo       

29-863 

29-749 

29-852 

29-788 

+  •011 

-•009 

§5     Galle 

29-859 

29-653 

29-843 

29-728 

+  •016 

-•075 

a  ■{  Hambantota            

29-809 

29-689 

29-811 

29-712 

-•002 

-•023 

■^     Batticaloa 

29-834 

29-761 

29-800 

29-711 

+  •034 

+  •050 

O  LTrincomalee            

29-611 

29-609 

29-636 

2^-637 

-•025 

-•028 

from  which  you  will  observe  that  there  was  a  certain  amount  of  disturbance  visibly 
recorded  on  these  days. 

I  am,  Sir, 

Your  obedient  Servant, 

J.  STODDART, 
Acting  Sunjeyor-Genercd  of  Ceylon, 
G.  J.  Symons,  Esq.,  Chairman^ 
Krakatoa  Committee, 

Royal  Society, 

London. 


INDIAN     OCEAN. 


Eye    Observations. 

In  none  of  the  islands  in  the  Indian  Ocean  are  tide  gauges  at  work.  Dr. 
Meldbtjm,  however,  has  collected  several  interesting  accounts  of  the  phenomena  of 
rise  and  fall  of  the  sea  at  Mauritius,  Seychelles,  Cargados  Garajos  and  Rodriguez^ 
which  are  given  in  full  below. 


CAPTAIN   WHARTON   ON  THE   SEISMIC   SEA  WAVES.  125 

Port  Louis,  Mauritius^ 

"  Opposite  the  gasworks,  on  the  southern  side  of  the  harbour  at  Port  Louis,  Mr. 
Darney  observed  that  the  sea  water  was  going  and  coming  the  whole  forenoon  of 
August  27th,  but  at  first  the  movement  did  not  attract  much  attention.  The  tide 
did  not  rise  as  usual,  and  it  was  difficult  to  bring  the  lighters  close  enough  to  the 
shore.  At  about  13  hrs.  30  mins.  the  water  came  with  a  swirl  round  the  point  of  the 
sea  wall,  and  in  about  a  couple  of  minutes  returned  with  the  same  speed.  This 
took  place  several  times,  the  water  on  one  occasion  rising  2^  feet.  The  water  was 
^ery  muddy  and  agitated,  and  quantities  of  jelly  fish  were  thrown  on  shore.  Similar 
phenomena  occurred  on  the  28th,  but  to  a  less  extent. 

"  On  the  northern  side  of  the  Trou  Fanfaron,  a  narrow  channel  on  the  north- 
eastern side  of  the  harbour  of  Port  Louis,  Captain  Ferrat  observed  at  some  time 
between  13  hrs.  30  mins.  and  14  hrs.  on  the  27th,  that  the  water,  which  was  then 
unusually  low,  suddenly  rushed  in  with  great  violence,  rising  fully  3  feet  above  the 
former  level.  An  alternate  ebb  and  flow  then  continued  till  nearly  19  hours,  and  the 
intervals  in  time  between  high  and  low  water  were  about  15  minutes.  There  was  no 
high  wave  or  billow,  but  strong  currents,  the  estimated  velocity  of  which  was  ftboiit 
3  knots  in  10  minutes,  or  18  knots  an  hour.  Vessels  moored  near  the  Dry  Docks 
swayed  much,  and  at  about  18  hrs.  30  mins.  one  of  the  hawsers  of  the  *  Touareg^ 
10  inches  in  circumference,  parted.  Buoys  in  the  neighbourhood  were  at  times  seen 
spinning  round  like  tops.  Disturbances  were  observed  on  the  28th  also,  and  there 
were  unusual  currents  even  on  the  29th. 

"  Another  observer,  Mr.  Isbesteb,  on  the  opposite  side  of  the  Trou  Fanfaron, 
noticed,  at  14  hours  on  the  27th,  that  the  water  around  the  '  5^cZZa,'  moored  within  a 
few  yards  of  him,  had  a  boiling  appearance.  Suddenly  the  water  receded  about 
20  feet,  leaving. some  boats  partlj'^  on  dry  land.  About  a  quarter  of  an  hour  after, 
the  water  rushed  back  and  advanced  about  6  feet  farther  inland  than  where  it  was  at 
14  hours.  The  water  then  receded,  and  a  series  of  oscillations  took  place,  lastmg  till 
at  least  18  hours.  The  intervals  between  high  and  low  water  were  from  15  to  20 
minutes,  and  the  range  of  rise  and  fall,  wiiich  at  first  was  about  3  feet,  gradually 
subsided  after  16  hours.  It  was  feared  that  the  warps  of  the  ^Stella'  would  give 
way.  Similar  phenomena  were  observed  on  the  28th,  and  to  a  small  extent  on 
the  29th. 

,  "The  Trou  Fanfaron  is  fi:om  200  to  300  feet  in  width,  and  about  1,600  in  length, 
running  nearly  east  to  west,  except  near  its  junction  with  the  main  harbour,  where  it 
trends  to  S.W. 

"As  far  as  I  can  ascertaii),  no  disturbances  were  observed  in  the  central  part 
of  the  main  harbour,  which  runs  nearly  S.E.  and  N.W.,  and  where  there  is  a  greater 
depth  of  water.     Nor  does  it  appear  that  any  were  observed  outside  the  harbour. 


126  CAPTAIN  WHARTON   ON   THE   SEISMIC   SEA   WAVES. 

Tomheau  Bay,  Mauritius. 

"  At  this  bay,  which  is  3^  miles  north  of  Port  Louis,  and  lies  east  and  west, 
the  sea  suddenly  receded  at  about  14  hours  on  the  27th,  and  numbers  of  fish  were 
caught  on  the  exposed  beach.  Some  time  after,  the  water  returned  with  great  force. 
A  series  of  oscillations  then  took  place. 

Arsenal  and  Turtle  Bays,  MauHtius. 

*'  Mr.  CoMMiNS  reports  that  in  the  bays,  which  are  l\  miles  north  from  Tombeau 
Bay,  and  which  also  lie  east  and  west,  similar  phenomena  commenced  about  noon  on 
the  27th,  and  lasted  till  at  least  17  hours  on  that  day,  the  sea  rising  and  falling  alter- 
nately to  the  extent  of  2  to  3  feet,  and  the  maximum  disturbance  occurring  at  about 
14  hours.  Between  the  two  bays  there  is  a  bar.  *  Arsenal'  being  the  outer,  and 
.*  Turtle '  the  inner  bay.  A  coaster  of  1 5  tons  burthen,  while  passing  at  14  hours  from 
Arsenal  to  Turtle  Bay,  stuck  on  the  bar ;  about  5  minutes  after,  the  sea  rushed  in 
from  Arsenal  Bay  and  sent  the  boat  flying  into  Turtle  Bay,  where,  after  having  made 
two  or  three  rapid  revolutions,  it  was  thrown  on  the  north  shore."' 

SoniUac,  Mauritius. 

**  In  this  harbour,  which  is  on  the  south  coast  of  Mauritius,  several  coasters  were 
driven  from  their  anchorage." 


*o^ 


The  most  remarkable  thing  to  be  noticed  in  these  reports  is  the  time  that  is 
stated  to  have  elapsed  between  the  crests  of  the  long  waves. 

This  is  said  to  be  about  30  or  40  minutes,  which  is  much  less  than  the  interval 
given  by  the  nearest  tide  gauges  at  the  South  African  ports,  but  more  than  the 
interval  of  the  Ceylon  waves.  From  the  position  of  Port  Louis,  on  the  western  side 
of  Mauritius,  or  that  farthest  removed  from  Java,  it  is  probable  that  the  waves  which 
passed  by  the  north  and  south  points  of  the  island  would  arrive  separately  at  the 
harbour,  and  that  the  phenomenon  was  doubled.  The  true  periodic  time  would  then 
be  from  60  to  80  minutes,  which  would  agree  better  with  the  diagrams. 

It  appears  possible,  therefore,  that  the  waves  here  recorded  were  the  long  wave^ 
felt  by  the  gauges.  The  Trou  Fanfaron  being  the  narrow  termination  of  the  funnel- 
shaped  harbour,  the  effect  of  the  wave  would  be  considerably  increased. 

The  time  of  the  arrival  of  the  first  wave,  given  at  about  14  hrs.  15  mins.  of  the 
27th,  corresponds  to  a  velocity  of  403  miles  an  hour  for  the  2,842  miles  that 
separate  the  1,000  fathom  line  off  Sunda  Strait  from  the  1,000  fathom  line  off 
Port  Louis. 


CAPTAIN    WHARTON   ON   THE    SEISMIC  SEA   WAVES. 


127 


This  is  a  higher  speed  than  is  given  by  other  observations,  but  it  is  to 
be  remarked  that  the  wave  selected  from  the  diagrams  of  self-registering  gauges 
for  comparison,  as  the  first  of  a  regular  series  of  higher  waves,  is.  generally 
preceded  by  other  distinct  though  smaller  undulations,  and  that  there  is  nothing 
in  these  eye  observations  at  Port  Louis  to  enable  such  comparatively  small 
distinctions  to  be  made ;  and  that  the  time  here  recorded  is  that  of  the  first 
disturbance  observed. 


Mah6,  Seychelles. 

**  Mr.  EsTRTDGE,  at  16  hours  on  the  27th,  saw  the  sea  rushing  in  at  the  rate  of 
about  4  miles  an  hour,  and  rising  to  the  extent  of  2  feet  range.  The  water  returned 
and  receded ;  and  this  flow  and  ebb  continued  all  night  and  all  next  day,  but  the 
action  was  quicker  and  the  rise  less.  From  10  hrs.  15  mins.  to  12  hrs.  5  mins.  on 
the  28th,  the  following  observations  were  made  in  a  channel  23  feet  wide  and  walled 
on  both  sides  : — 


Rise 

Rise 

Time. 

Water  ran. 

in 
inches. 

Time. 

Water  ran. 

in 
inches. 

h.     m. 

h.     m. 

10     15 

Water  ran  ont 



Noon 

Water  ran  in. . 

10 

10    27 

„          in.  • 

10 

12     10 

„          out 

— 

10    35 

„          ont 

— 

12     25 

in. . 

10 

10    40 

in. . 

10 

12     27 

ont 

— 

10    50 

„          ont 



12    45 

in.. 

10 

11     20 

„          in. . 

3 

12    50 

ont 

— 

11     25 

„          ont 



12    55 

„          in.  • 

10 

11     30 

„          in. . 

10 

13    05 

ont 

— 

11     40 

oat 

— 

According  to  these  observations,  the  mean  interval  in  time  between  the  epochs 
of  high  water  was  21  minutes.  Mr.  Estridge  says  that  the  action  continued 
throughout  the  rest  of  the  28th,  and  also  during  a  part  of  the  29th,  but  less 
frequently. 

The  height  of  the  waves  is  less  than  those  observed  at  Mauritius,  but  the 
journey  over  the  long  and  shallow  Seychelles  bank  probably  killed  the  wave.  These 
seem  to  be  short  waves  similar  to  those  observed  in  Ceylon. 

The  time  here  mentioned  by  Mr.  Esthidge  would  give  373  miles  an  hour  for  the 
2,873  miles,  measured  from  the  1,000  fathom  hne  off  Sunda  Strait  to  the  outer 
soimding  on  the  edge  of  the  Seychelles  bank,  of  200  fathoms,  which  is,  however, 
probably  nearly  identical  with  the  1,000  fathoms,  as  the  bank  is  steep. 

s  2 


128  CAPTAIN  WHARTON   ON   THE   SEISMIC    SEA   WAVES. 

Cargados  Garajos. 

"  On  August  27th,  the  *  Evelina/  Captain  Elault,  was  at  anchor  on  the  west- 
north-west  coast  of  Avocaire  Island  (one  of  the  St.  Brandon  islands,  which  are 
between  16°  15'  and  16°  57'  S.,  and  58°  41'  and  59°  26'  E.)  in  3f  fathoms,  a  cable  s 
length  off  shore.  At  15  hours  on  that  day  it  was  observed  that  the  sea  suddenly 
advanced  about  20  feet  beyond  the  highest  water-mark.  As  it  was  then  ebb  tide 
this  phenomenon  appeared  very  strange.  The  water  soon  receded  with  a  rapid 
motion,  and  the  shoal  patches  appeared  quite  dry  to  a  very  long  distance  from  the 
island  Before  fifteen  minutes  had  elapsed,  the  water  rose  again  with  the  same 
velocity,  coming  up  to  the  first  mark.  It  was  not  a  wave,  nor  a  billow,  nor  a  high 
sea  ;  the  water  was  smooth,  except  where  there  were  heads  of  coral,  and  there  only  a 
few  wavelets  were  formed.  This  to  and  fro  motion  lasted  up  to  19  hours;  at  first 
the  intervals  between  high  and  low  water  were  about  10  minutes,  and  towards 
18  hours,  20  minutes.  The  current  was  setting  towards  E.N.E.  of  the  compass  at 
the  rate  of  ten  miles  an  hour.  The  sea  was  not  rough  outside,  nor  at  the  anchorage, 
nor  eight  miles  N.N.W.  from  it,  where  two  boats  had  been  fishing  from  morning  till 
14  hours.  At  a  quarter  of  a  mile  from  Avocaire,  these  boats  were  caught  at  16 
hours  by  the  receding  tide,  and  left  high  and  dry  for  10  minutes.  Similar  phe- 
nomena occurred  between  4  hours  and  7  hours  on  the  28th,  but  they  were  less 
intense  ;  and  only  four  alternate  motions  of  the  se^- water  were  observed.'' 

Here  also  the  periods  of  the  waves  are  reported  as  small,  from  20  to  40  minutes. 
The  20  feet,  mentioned  as  being  the  distance  above  high  water-mark,  to  which  the 
wave  reached,  would  on  the  flat  sandy  shores  of  the  island  correspond  to  perhaps 
18  inches  or  2  feet  of  vertical  height.  The  speed  calculated  from  the  recorded  time 
of  15  hours  would  be  370  miles  an  hour  for  the  2,662  miles,  measured  from  the  1,000 
fathoms  off  Sunda  to  the  outer  sounding  of  40  fathoms  off  Cargados. 


Port  MathuHn,  Rodiiguez. 

"  Serjeant-Major  Walus  observed  at  13  hrs.  30  mins.  on  August  27th,  a  peculiar 
appearance  of  the  sea-water  in  the  inner  harbour.  It  was  then  ebb  tide,  and  most 
of  the  boats  were  aground.  The  sea  looked  like  water  boiling  heavily  in  a  pot,  and 
the  boats  which  were  afloat  were  swinging  in  all  directions.  The  disturbance 
appeared  quite  suddenly,  lasted  about  half  an  hour,  and  ceased  as  suddenly  as  it  had 
commenced.  At  14  hrs.  20  mins.  a  similar  disturbance  began  ;  the  tide  all  of  a  sudden 
rose  5  feet  11  inches,  with  a  current  of  about  10  knots  an  hour  to  the  westward, 
floating  all  boats  which  had  been  aground,  and  tearing  them  from  their  moorings. 
All  this  happened  in  a  few  minutes.  The  tide  then  turned  with  equal  force  to  the 
eastward,  leaving  the  boats  which  were  close  in-shore  dry  oh  the  beach,  and  dragging 


CAPTAIN   WHARTON   ON  THE   SEISMIC   SEA  WAVES.  129 

the  Government  boat  (a  large  decked  pinnace)  from  heavy  moorings,  and  leaving  it 
dry  on  the  reefe.  The  inner  harbour  was  almost  dry.  The  water  in  the  channel  was 
several  feet  below  the  line  of  reefs  j  and,  owing  to  the  sudden  disappearance  of  the 
water,  the  reefs  looked  like  islands  rising  out  of  the  sea.  The  tides  continued  to  rise 
and  fall  about  every  half  hour,  but  not  so  high,  or  with  the  same  force,  as  the  first 
tide.  By  noon  on  the  29th,  the  tide  was  about  its  usual  height,  and  appeared  to  be 
settled.  The  water  was  very  muddy,  and  not  nearly  so  salt  as  sea-wate^  usually  is ; 
it  was  little  more  than  brackish." 

Here  the  wave  of  14  hrs.  20  mina  is  stated  to  be  the  first  high  one,  and  is 
therefore  taken  for  comparison. 

The  velocity  of  the  wave  would,  therefore,  be  376  miles  for  the  distance  of 
2,519  miles  from  the  1,000  fathom  line  from  Sunda  Strait  to  the  outer  sounding  of 
200  fathoms  on  the  eidge  of  the  steep  bank  off  Rodriguez  Island. 

The  height  of  5  feet  1 1  inches  appears  precise,  but  it  is  so  large  compared  with 
other  records  at  places  at  this  distance  from  Krakatoa,  that  some  doubt  is  permissible 
as  to  its  correctness.  It  is  not  stated  how  it  was  measured,  and  from  my  personal 
knowledge  of  the  island  and  of  its  flat,  fringing  reefs,  1  think  that  an  eye  estimation 
would  be  liable  to  considerable  error,  and  I  do  not  fancy  that  any  gauge  has  been 
erected  since  my  visit  in  1874. 

The  remark  on  the  brackishness  of  the  wat6r  may  be  taken  as  evidence  of  the 
imagination  of  the  observer. 


SOUTH  AFRICA  AND  THE  ATLANTIC. 


Tidal  Diagrams. 


Port  Alfred. 

The  first  of  the  more  distant  tide  gauges  is  that  at  Port  Alfred,  in  South  Africa, 
4,624  miles,  with  an  uninterrupted  sweep  from  Krakatoa.  This  gauge,  although 
placed  inside  a  bar,  gives  a  very  good  diagram.  It  is  on  the  scale  of  1^  inches  to 
the  foot,  and  1  inch  to  the  hour.  The  curve  is  quite  smooth  to  7  hrs.  on  the  27th, 
when  an  irregular  oscillation  commences  sharply.  This  gradually  increases  to  a 
height  of  6  inches,  when  a  distinctly  higher  wave,  of  a  height  of  1  foot  4  inches, 
is  shown  at  17  hrs.  10  mins. 

Eleven  waves  of  an  average  interval  of  65  minutes  can  then  be  traced,  although 
their  height  is  much  varied  by  interference.     One  cannot  be  sure  that  the  17  hrs. 


130  CAPTAIN   WHARTON   ON  THE   SEISMIC    SEA   WAVES. 

10  mins.  wave  is  that  which  should  he  taken  as  corresponding  to  the  10  o'clock  wave 
from  Krakatoa^  hut  it  is  apparently  the  commencement  of  a  fresh  series  of  waves, 
no  period  of  former  waves  falling  in  with  it,  and  I  have  therefore  selected  it  as  the 
comparison  wave.     The  waves  in  this  series  are  as  follows  : — 


Times    . . 

h.     m.            h.      111.            h.     m. 

17  10       18  17       19  22 

h.     m. 

20  30 

h.      nu 

21  28 

h. 

22 

m. 

44 

Intervals  . 

m.                   in. 

67             65 

m. 

68 

m.                  m. 

58             76 

m. 

64 

Times    . . 

23  48          1   01          2  03 

2  55 

4  06 

5 

05 

Intervals  . 

73             62 

52 

71             59 

double  intervals  will  be  : — 

n.    m.            h.     m.             h.    m. 

2  12         2  06          2  20 

h.    m. 

2  15 

h.    m. 

2  03 

The  distance,  measured  from  the  1,000  fathom  line  off  Sunda  Strait  to  the  1,000 
fathom  line  off  Port  Alfred,  is  4,550  miles,  and  the  velocity  for  the  17  hrs.  10  mins^ 
wave  will  be  388  miles  an  hour*  This  corresponds  to  a  depth  of  2,245  fathoms, 
which  is  probably  not  far  from  the  truth,  though  the  few  soimdings  which  exist  on 
the  route,  are  all  over  2,500  fathoms. 

1'he  first  wave  that  appears  at  all,  which  is  very  well  marked  at  7  lirs.  09  mins. 
on  the  27th,  can  be  followed  for  twelve  undulations  thus  : — 

h.    m,  h.    m.  h.    in.  h.      ni.  h.     m.  h.     m. 

Times    ,.      7  09         8  18         9  29       10  40         11  50       13  02 

m.  m.  m.  m.  m.  m. 

Intervals  .  69  71  71   .  70  72  69 

Times    . ,    14  11       15  20       16  35       17  45  miss  20  10       21  28 
Intervals .  69  75  70  145  78 

The  mean  interval  is  71  minutes. 

The  second  wave,  at  7  hi-s.  21  mins.,  can  be  followed  still  further  for  seventeen 
undulations,  with  a  mean  interval  of  77  minutes,  as  folioM^s  : — 


Times    .. 

h.    ni.             h.     m.               h.     m.            li. 

7  21          8  38           y  57       11 

m.            h.    m.               h.     nu 

16       12  35         13  41 

Intervals . 

m.                       m.                   ni. 

77               79            79 

m.                  m.                     m. 

79              66               71 

Times    .  , 

14  52       16  07  miss  18  33       19 

52       21   11  miss  23  49 

Intervals . 

75               146           79 

79            158              74 

Times     . . 

1  03         2  23  miss  5  04 

Intervals . 

80              161 

CAPTAIN   WHARTON  ON  THE   SEISMIC   SEA   WAVES.  131 

The  second  series  of  large  waves,  which  commences  with  one  at  18  hrs.  33  mms., 
can  be  followed  for  ten  undulations,  with  a  mean  interval  of  55  minutes,  843 
follows : — 


Times 

h. 
18 

m. 

33 

h.      m.              li.     m.                h,     m.              h.      m. 

19  23         20   14         21   12         22  08 

Intervals  . . 

xn. 

50 

m.                      m.                      aft.                     m. 

r.l               58               56               56 

Times 

23 

04 

24  00  miss  1  52  miss  3  47 

Intervals  . . 

m. 

56 

m.          '            m. 

112               115 

It  will  be  seen  that  none  of  these  series  but  that  first  given  will  coincide  with 
the  wave  at  17  hrs.  10  mins. 

The  maximum  wave  is  at  23  hours  on  August  27th,  with  a  height  of  1^  feet ; 
and  the  disturbance  continues  to  10  hours  of  tiie  29th  of  August 

The  complications  of  waves  make  this  one  of  the  most  difficult  diagrams  to  deal 
with.  To  what  are  these  earlier  waves  attributable  ?  This  diagram  should  afford  a 
clue,  as  the  abruptness  of  the  first  appearance  of  the  disturbance  at  7  hrs.  09  mins. 
deserves  remark,  and  differs  from  other  diagrams. 

But  supposing  the  speed  generally  deduced  from  the  waves  to  be  approxi- 
mately correct,  the  wave  that  caused  this  first  disturbance  must  have  left  Krakatoa 
at  about  23  hrs.  30  mins.  on  the  26th,  local  time,  at  which  time  there  is  no  record 
of  a  wave  of  any  height  in  the  Strait  of  Sunda,  The  wave  from  Krakatoa  of 
1  hr.  42  mins.  of  the  27th  was  recorded  faintly  on  the  diagram  at  Batavia,  but  this 
wave  was,  from  the  absence  of  corresponding  damage  effected  on  the  coast  near  the 
volcano,  a  small  one,  and  it  is  hardly  to  be  supposed  that  it  could  show  so  sharply 
on  the  Port  Alfred  gauge.  Supposing,  however,  that  the  7  hrs.  09  mins.  wave  is 
due  to  the  1  hr.  42  mins.  wave,  from  Krakatoa,  it  travelled  at  a  rate  of  424  miles 
an  hour. 

Port  Elizabeth. 

The  Port  Elizabeth  gauge  diagram  is  not  satisfactory,  the  tracing  having  been 
very  carelessly  made,  so  that  the  hour  lines  are  very  inaccurate. 

The  scale  is  1  inch  to  the  foot,  and  1  inch  to  the  hour. 

The  gauge  is  much  more  exposed  than  that  at  Port  Alfred,  and  feels  the  local 
waves  more. 

The  diagram  at  noon,  August  26th,  begins  with  continuous  oscillations  of  a  few 
inches,  which  get  slightly  larger  till  16  hours  of  the  27th,  when  two  waves  of  9  inches 
height  follow  one  another  at  1^  hours  interval. 

At  19  hrs.  54  mins.  comes  an  unmistakably  large  wave  of  4  feet  range,  which  I 
take  for  the  comparison  wave. 


1 


132  CAPTAIN   WHARTON  ON   THE    SEISMIC    SEA  WAVES. 

The  disturbance  is  henceforth  well  marked  with  apparently  but  littie  interference, 
but,  nevertheless,  the  intervals  of  series  of  waves  do  not  come  out  well.  Six  waves 
follow  the  comparison  wave  with  periods  of  70  minutes.  Afterwards  they  cannot 
be  satis&ctorily  followed  for  about  6  hours,  when  the  same  period  can  again  be 
recognised. 

Starting  with  the  same  wave  at  1 9  hrs.  54  mins.,  twenty-two  waves  can  be  taken 
with  an  average  period  of  2  hrs.  24  mins. 

The  19  hrs.  54  mips,  series  is  as  follows  :— 

h.     xn.  h.     m.  h.     m.  h.     m.  h.    m.  h.    m. 

Times       ..      19  54         21  04         22  14  miss  0  33         1  46         2  57 

m.  m.  m.  .  in.  m. 

Intervals..  70  70  139  .73  71 

The  distance,  measured  from  the  1,000  fathom  line  off  the  Strait  of  Suhda  to 
the  1,000  fathom  line  off  Port  £lizabeth,  is  4,611  miles,  for  which  the  19  hrs. 
54  mins.  wave  gives  a  velocity  of  3-20  miles  an  hour.  The  speed  for  Port  Alfred, 
only  a  few  miles  eastward,  is  388  miles,  and  therefore  these  discordant  results  cannot 
be  considered  satisfactory,  as  Port  Elizabeth  would  give  a  mean  depth  of  1,505 
fathoms,  whereas  Port  Alfred  gives  2,245  fathoms;  the  track  of  the  waves  lying  dose 
to  one  another. 

It  is  not  possible  to  make  them  agree  without  straining  the  evidence,  if  the 
comparison  wave  be  selected  as  being  the  first  of  a  comparatively  regular  series  ;  but 
if  the  17  hrs.  52  mins.  wave  be  taken,  which  might' be  done  by  a  mere  eye  selection, 
the  speed  of  the  wave  would  stand  at  371  miles,  which  would  agree  better  with  the 
adjacent  gauges  of  Port  Alfred  and  Table  Bay. 

The  series  of  longer  periods,  starting  with  the  19  hrs.  54  mins.  wave,  is  as 
follows  : — 


Times     . 
Intervals 

Times    . 
Intervals 

Times     . 
Intervals 

Times    . 
Intervals 


Ii.     m.  h.     m.  h.    m.  h.     m.  h.      m.  h.      ni. 

19  54  22  12  0  33  3  00  5  25  7  38 


h.    m. 

h.     m. 

h.    m. 

h.     m. 

h.    m. 

h.    m. 

2  18 

2  21 

2  27 

2  25 

2  13 

2  22 

10  00           12  20         14  37  17  20         1942         22  lO 

2  20              2   17            2  43            2  22            2  28            2  26 

0  36             2  50           5  37  8  04         10  22      .    12  40 

2  14             2  47           2  27           2  18           2  18           2  23 

15  03            17  28          19  54  22  04 

2  25             2  26           2  10 


Twenty-two  waves  in  all,  with  a  mean  period  of  2  hrs.  23  mins. 

In  connection  with  the  disturbance  at  Port  Elizabeth,  the  following  letter  fi'ofn 


CAPTAIN   WHARTON   ON   THE   SEISMIC   SEA  WAVES.  133 

the  Captain  of  one  of  the  large  mail  steamers  then  laying  in  the  bay  is  interesting, 

as  showing  that  horizontal  movement^  and  that  of  a  rapid  character,  was  taking 

place  at  the  time  the  larger  waves  began  to  arrive  : — 

"  The  'Hawarden  Castle '  was  at  anchor  in  Algoa  Bay  with  starboard  anchor  and 

60  fathoms  of  chain,  the  anchor  being  in  6f  fathoms.     At  about  8  hrs.  30  mins.  p.m. 

on  the  27th  of  August,  wind  S.E.,  moderate  breeze  with  a  little  sea,  ship  riding  head 

to  wind,  1  observed  the  ship  suddenly  swing  with  head  to  N.E.,  bringing  wind  and 

sea  abeam.     My  first  impression  was  that  our  cable  had  parted,  but  on  going  forward 

I  found  a  heavy  strain  on  the  cable  caused  by  the  anchor  still  bearing  S.E.  from  the 

ship.     So  heavy  was  the  strain  that  the  friction  brake,  by  which  we  always  ride,  and 

which  is  powerful  enough  to  part  the  cable,  would  not  hold.     I  at  once  dropped  the 

second  anchor,  and,  on  paying  out  cable,  the  ship  seemed  to  drift  bodily  to  the  N  .W,, 

her  head  still  pointing  to  the  N.E.     When  we  had  an  equal  strain  on  both  cables,  I 

had  time  to  remark  to  the  chief  oflScer  the  strangeness  of  the  occurrence,  and  while 

speaking  (about  8  hrs.  50  mins.  p.m.),  the  ship  again  turned  round  with  her  head  to 

wind  and  sea  (S.E.).     We  remained  in  this  position  about  8  minutes,  when  we  again 

swung  with  head  to  N.E.,  but  on  this  occasion  more  slowly  than  at  first.     From  this 

hour  till  midnight  we  occasionally  headed  the  wind  and  sea,  but  only  for  a  short  time, 

when  back  we  went  again,  head  N.E.,  with  wind  and  sea  abeam.     After  midnight 

the  wind  got  very  light,  and  at  3  hours  a.m.  we  were  heading  the  S.E.  swell  in 

a  calm. 

•*  (Signed)        M.  P.  Webster." 

This  swinging  of  the  ship  means  that  a  current  was  setting  out  from  the 
shore. 

Now,  the  time  here  recorded,  8  hrs.  30  mins.  p.m.,  is  just  midway  between 
the  times  of  arrival  of  the  first  and  second  crests  in  the  series  taken  for 
comparison ;  and  therefore  the  water  would  be  retreating  from  the  coast  and  setting 
seaward. 

Table  Bay. 

This  diagram  is  a  good  one,  but  the  gauge  is  evidently  influenced  by  small  local 
waves.     The  scale  is  one  inch  to  the  foot,  and  half  an  inch  to  the  hour. 

The  first  large  wave  is  well  marked,  though  the  oscillation  before  it,  is  somewhat 
higher  than  those  preceding. 

The  greater  waves  are  ushered  in  by  small  undulations  for  some  hours ;  then 
comes  a  large  wave,  of  9  inches  range,  at  18  hrs.  42  mins.  of  the  27th,  followed  by  a 
etill  larger  series  of  18  inches.  These  cannot  be  followed  for  more  than  12  hours, 
interferences  preventing  identification,  though  the  disturbance  continues  to  19  hours 
of  the  29  th  of  August. 

As  the  18  hrs.  42  mins.  wave  falls  in  very  well  with  the  period  of  the  succeeding 

T 


134  CAPTAIN   WHARTON  ON  THE   SEISMIC   SEA  WAVES. 

series,  I  have  taken  it  for  comparison.     The  series  is  of  13  waves  with  a  mean  period 
of  62  minutes,  and  a  period  for  the  double  waves  of  2  hrs.  05  mins. 


h,     m.             h.     m.             h.     m.             h.     m.              h.      m.             h,     m.             h.     m. 

Times 

18  42         19  50         20  53         22  05         23  07         23  58         0  52 

ui.                    m.                     m.                     m.                     m.                     m»                   m. 

Intervals . . 

68               63               72               62               51               54             68 

Times 

2  00           2  50           3  58           5  00           6  18           7  12 

Intervals  . . 

50               68               62               78               54 

There  is  no  interference  so  far,  nor  any  second  series.  In  this  respect  the 
diagram  greatly  differs  from  those  of  Port  Elizabeth  and  Port  Alfred. 

The  gauge  is  situated  inside  the  breakwater,  and  the  wave  would,  in  coming  into 
it,  have  passed  round  a  complete  circle  from  its  original  course  from  Krakatoa. 

The  tracks  followed  by  the  waves  to  these  three  South  African  ports  are  not 
identical,  though  they  do  not  lie  far  apart,  and  are  sufficiently  near  to  enable  us  to 
assume  that  the  mean  depth  passed  over  by  the  separate  waves  is  not  far  from  the 
same.  The  Port  Alfred  wave  would  give  a  depth  of  2,245  fathoms  ;  that  to  Port 
Elizabeth  1,505  fathoms;  and  the  Table  Bay  wave  2,010  fathoms.  These  are  all  for 
the  deep  water  portion  of  the  tracks,  starting  from  the  assumed  position  of  the 
1,000  fathom  line  off  the  Strait  of  Sunda,  to  the  same  depth  off  the  South  African 
ports.  As  imfortunately  the  sounding  of  the  Indian  Ocean  is  very  incomplete,  it 
cannot  be  certainly  stated  from  actual  observation  what  the  true  mean  depth  is ;  but 
as  all  the  soundings  yet  obtained  on  the  line  of  the  wave  are  over  2,500  fathoms, 
it  may  be  assumed  to  be  in  all  probability  not  less  than  2,300  fathoms.  On  this 
assumption  the  Port  Alfred  record  agrees  fairly  with  the  time  calculated  from  the 
formula,  but  the  Port  Elizabeth  and  Table  Bay  waves  are  too  late. 

Fort  Molthi. 

At  Port  Moltke,  in  the  inland  of  South  Georgia,  a  tide  gauge  was  working  under 
the  supervision  of  the  German  South  Polar  Expedition. 

The  scale  is  2'^'1  inches  to  a  foot,  and  0'8  inch  to  an  hour. 

This  position  is  well  open  to  the  sea.  The  diagram  is  good,  but  presents  great 
difficulties. 

After  small  oscillations  of  3  inches,  a  larger  wave  of  11  inches  suddenly  appears 
at  14  hrs.  29  mins.  of  the  27th.  This  is  followed  by  three  other  waves  with  a  mean 
period  of  63  minutes  ;  after  which  the  regularity  is  lost. 

h.      m.  h.      m.  h.      m.  h.     m. 

Times  . .  . .  14  29         15  42         16  45         17  40 

m.  m.  m. 

Intervals     •.  ,.  73  63  55 


CAPTAIN  WHAHTON  ON  THE  SEISMIC   SEA  WAVES.  135 

If  the  first  of  the  series  be  taken  for  th^  comparison  wave,  it  gives  an  average 
speed  of  487  miles  an  hour  from  Krakatoa,  which  I  cannot  but  think  is  extremely 
improbable,  corresponding  as  it  does  with  a  depth  of  3,500  fathoms. 

These  undulations  diminish  after  21  hours,  but  at  1  hr.  45  mins.  on  the  28th 
another  wave  of  1 5  inches  is  recorded,  which  is  followed  by  others  for  20  hours. 
These  waves  are  complicated  and  apparently  belong  to  two  series  of  about  the  same 
period.     The  first  series  of  62  minutes  period  is — 

b.    m.  h.    ID.  h.    m.  h.    in.  h.    m.  h.    m.  h.    m.  h.     m. 

Times       . .      1  44         2  46         3  47         4  45         5  48         6  51         8  07         9  07 

m.  m.  m.  m.  m.  in.  m. 

Intervals..  62  61  58  63  63  76  60 

Times       ..    10  00       11  08       12  03       12  56       13  55       14  53       16  08 

Intervals  53  68  55    .        53 "  59  58  75 

The  double  interval  is  2  hrs.  3  mins. 

The  second  series  of  a  mean  period  of  63  minutes  is — 


h.    m.            h.    m.            h.    m.            h.    m.             h«    m.             h.    in.           h.    m. 

Times       . . 

..    2  20         3  25         4  21         5  21         6  18         7  22         8  28 

m.                   m.                  m.                   m.                   m.                   m.                    m. 

Intervals . . 

65             56             60             57             64             66             65 

Times 

..    9  33       10  41       11  40       12  39       13  44       14  47       15  55 

Intervals  , . 

68             59             59             65             63             68             65 

Tunes       .. 

. .  17  00       17  55       19  12       20  15 

Intervals . . 

mi   _    J       11 

55             77             63 

_     •      1                 1    •       ^    1               ^          • 

The  double  interval  is  2  hrs.  6  mins. 

If  we  take  the  wave  at  1  hr.  44  mins.  for  comparison,  the  speed — calculated  for 
the  distance  from  the  1,000  fathom  line  off  Sunda  Strait  to  the  100  fathom  line  off 
Port  Moltke,  which  is  6,619  miles — is  266  miles  an  hour.  This  is  apparently  as  low 
as  the  other  speed  calculated  firom  the  first  large  wave  at  14  hrs.  29  mins.  of  the 
27th  is  high  ;  but  the  track  foUowed  by  the  wave  from  Sunda  Strait  passes  in  one 
place  south  of  the  Kerguelen  Group,  where  soundings  of  160  fathoms  have  be6n 
obtained,  and  afterwards  passes  through  the  pack  of  Antarctic  ice  for  many  miles ;  so 
that  retardation  may  not  unreasonably  be  assxuned,  as  the  depths  are  probably  not 
great  on  this  course. 

To  what  cause  the  earlier  waves  are  to  be  attributed  I  am  unable  to  suggest,  as 
the  duration  of  a  regular  series  is  not  long.     The  period  is  not  unKke  that  recognised 

t2 


136  CAPTAIN  WHARTON   ON  THE  SEISMIC   SEA  WAVES. 

in  so  many  of  the  diagrams  discussed,  and  visible  in  the  later  series  of  waves  on 
this  gauge. 

Altogether  the  results  from  this  station  are  not  satisfactory.  Dr.  Neumayer, 
the  Director  of  the  Deutsche  Seewarte,  Hamburg,  has  assured  me  that  there  is  no 
error  in  the  times  used. 

Orange  Bay,  Cape  Horn. 

The  French  Meteorological  Expedition  had  an  automatic  tide  gauge  at  work  at 
Orange  Bay.  The  photographic  copies  fiu-nished  are  very  small,  but  I  have  had 
them  enlarged  by  photography  for  purposes  of  measurement. 

This  is  an  interesting  diagram,  and  seems  to  indicate  that  two  distinct  series  of 
waves  arrived,  one  five  hours  before  the  other. 

The  south  pole,  with  its  unknown  lands,  but  more  or  less  known  icy  barriers, 
intervenes  between  the  Strait  of  Sunda  and  Cape  Horn.  Thus  a  wave  would  have 
to  travel  round  these  obstructions,  and  would  pass  on  both  sides,  the  distance  by  the 
west  being  about  7,520  miles,  and  by  the  east  about  7,820. 

I  have  come  to  the  conclusion  that  the  earliest  waves  were  those  that  travelled 
the  greatest  distance,  for  the  following  reasons  : — 

A  careful  examination  shows  that  the  eastern  wave  is  unfettered  by  islands,  and 
that  the  sea  from  the  few  known  depths  is  probably  deep.  By  the  other  route,  on 
the  contrary,  the  Kerguelen  Group  is  passed,  and  hereabouts  the  depths  do  not 
exceed  200  fathoms ;  also  on  passing  between  the  Sandwich  Land  and  South  Georgia 
a  more  or  less  shallow  sea  is  in  all  probability  travelled  over. 

The  course  of  the  western  wave  is,  for  the  greater  part  of  the  distance,  identical 
with  that  which  reached  South  Georgia,  in  which  case  we  have  seen  that  its  speed  was 
probably  low.  If  the  early  waxes  are  taken  to  be  those  .which  passed  south  of  South 
Georgia,  it  will  appear  that  they  arrived  at  Orange  Bay  1^  hours  earlier  than  at 
South  Georgia,  which,  seeing  that  the  distance  is  850  miles  greater,  seems 
impossible. 

The  gauge  was  situated  in  a  bay  inside  a  good  many  islands,  which  would  tend 
to  impede  the  wave  and  cause  irregularities. 

The  diagram  shows  small  and  irregiJar  disturbance  from  the  commencement,  but 
at  21  hrs.  57  mins.  on  the  27th  there  is  the  first  of  a  short  series  of  four  waves  with 
a  period  of  37  minutes  as  follows  : — 

h.      m.  h.      m.  h.      m.  h.      m. 

Times  . .  . .  21  57  22  37  23  13  23  47 

m.  m.  in. 

Intervals  ..  40  36  34 

Another  wave  follows,  but  at  54  minutes  interval.     The  disturbance  then  dies  down. 


CAPTAIN  WHARTON  ON  THE   SEISMIC   SEA  WAVES.  137 

but  at  4  hrs.  57  mins.  on  the  28  th  there  is  the  first  of  a  second  series  of  eleven 
waves,  with  a  mean  period  of  36  minutes,  as  follows  : — 

h.    m.  h.    m.  h.    m.  h.    m.  h.    m.  h.    m. 

Times  ..  , .      4  57         5  32         5  58  6  33  7  06         7  46 

m.  m.  m.  m.  in.  m. 

Intervals  ..  35  26  35  33  40  30 

Times  ..  .  .      8  16         8  57         9  37         10  15         11  00 

Intervals  .  .  41  40  38  45 

The  maximum  height  of  the  waves  is  7  inches,  occurring  at  the  third  wave  of 
the  first  series.  The  speed  of  the  first  series,  taken,  as  I  have  said,  by  the  eastern 
route,  is  347  miles  an  hour;  of  the  second,  by  the  western  route,  251  miles  ;  which 
agrees  very  fairly  with  that  of  the  South  Georgia  wave,  and  tends  to  show  that 
this  conclusion  is  correct.  The  diagram  shows  disturbance  till  the  end,  viz.,  until 
noon  on  the  29th,  but  this  is  irregular  and  probably  due  to  local  causes. 

If  these  waves  are  due  to  Krakatoa,  they  seem  to  be  again  broken  up,  as  the 
mean  period  is  roughly  half  of  that  noted  on  former  diagrams. 

For  the  second  and  longer  series,  the  double  intervals  are  : — 

61     68     70     81     83,  or  a  mean  of  73  minutes. 


Colon,  Isthmtis  of  Panama. 

The  Colon  diagram  presents  features  utterly  unlike  any  other  of  the  gauges 
under  discussion,  at  a  distance  from  the  Strait  of  Sunda. 

Commencing  very  sharply  and  distinctly,  a  negative  wave  of  5  inches  is  followed 
by  a  positive  wave  of  13  inches  range,  the  first  of  a  series  of  sixteen  waves  with  a 
period  of  70  minutes,  remarkably  regular,  with  no  sign  of  interference,  and  gradually 
dying  away  in  a  manner  difierent  from  all  others  recorded. 

The  time  of  arrival  of  the  first  wave  is  16  hrs.  30  mins.,  which  gives  a  speed  of 
026  miles  an  hour. 

As  this  corresponds  to  a  mean  depth  from  the  Strait  of  Sunda  of  over  5,000 
fathoms,  and,  over  the  greater  part  of  the  distance,  the  depth  is  known,  and  is  about 
2,400  fiithoms, — this  result  may  be  regarded  as  out  of  the  question ;  and  the 
waves  which  disturbed  the  Colon  gauge  must  be  ascribed  to  some  other  cause  than 
Krakatoa. 

As  the  whole  of  the  coast  on  which  Colon  lies  is  subject  to  rollers  of  various 
dimensions,  which  set  in  from  the  Caribbean  Sea,  with  no  corresponding  local  change 
of  wind,  it  appears  that  the  origin  of   these  waves  may  be  sought  in  some  such 


138  CAPTAIN  WHARTON  ON   THE   SEISMIC   SEA   WAVES. 

direction,  with  much  less  improbability  than  by  imagining  that  an  undulation  starting 
from  Krakatoa  could  have  travelled  to  Colon  in  18  hours,  more  especially  as  the 
arrival  of  the  wave  at  Table  Bay  in  13^  hours  necessitates  its  having  travelled  the 
remaining  distance,  6,380  miles,  in  under  5  hours,  or  at  a  velocity  of  over  1,000  miles 
an  hour. 


EUROPE. 

Socoa. 

This  harbour,  situated  in  the  Bay  of  Biscay  near  the  boundary  of  France  and 
Spain,  is  the  nearest  place  to  the  northward  of  the  Cape  of  Good  Hope  at  which  an 
automatic  tide  gauge  was  at  work.  The  small  photographi3  reductions  of  the  tidal 
diagrams  have  been  enlarged  three  times  by  photography,  and  from  them  the 
measurements  are  taken ;  the  same  course  has  been  pursued  in  dealing  with  the 
diagrams  for  Rochefort,  Cherbourg,  and  Havre. 

A  disturbance,  which  though  small  is  quite  distinct,  and  fairly  regular,  appears 
at  4  hrs.  50  mins.  on  the  28th,  and  lasts  10  hours.  Seven  undulations  can  be 
followed  with  a  mean  period  of  39  minutes. 

h.     m.  h.    m.  h.    m.  h.    m.  h.  •  m.  h.    m.  h.    m. 

Times  . .  . .      4  50         5  25         6  13         6  45         7  27         8  04         8  42 

in.  m.  m.  m.  m.  m. 

Intervals  .  .  35  48  32  42  37  38 

The  range  does  not  exceed  3  inches.  Taking  the  first  wave  at  4  hrs.  50  mins., 
the  speed  for  a  distance  of  10,729  miles  is  425  miles  an  hour. 

Rochrfurt. 

This  gauge  is  situated  10  miles  up  the  Charente  River,  but  the  converging 
character  of  the  shores  of  the  Basque  Roads  would  tend  to  magnify  the  waves. 

Four  can  be  traced  with  a  mean  interval  of  55  minutes  as  follows,  on  the  28th 
of  August : — 

b«    m.  h.     in*  h.     m.  h.     m. 

Times  ,.940  1035  1128  1225 

in.  m.  m. 

Intervals   ....  55  53  57 

The  range  of  the  third  wave  is  5  inches.  The  distance  is  1 0,724  miles,  which 
gives  a  speed  of  414  miles  an  hour. 


CAPTAIN  WHARTON  ON  THE   SEISMIC   SEA   WAVES.  139 

Cherbourg. 

The  disturbance  on  this  diagram  is  short.  The  first  wave  appears  at  9  hrs. 
20  mins.  on  the  28th  and  is  followed  bj  four  others,  of  an  average  range  of  2 
inches  : — 

h.     m.  h.     m.  h.      in.  h.      m.  h.      m. 

Times  ..  . .      9  20  9  59  10  32  11  07  11  44 

m.  m.  in.  m. 

Intervals  ..  39  33  35  37 

The   mean  period  is    36  minutes.  The   distance   from  the  1,000  fathom   line 

off  the  Strait  of   Sunda  to  the   1,000  fathom  line   at   the  mouth  of  the  English 

Channel,  is  10,780  miles.     The  9  hi-s.  20  mins.  wave  gives  a  speed  of  421  miles 
an  hour. 

Havre. 

This  gauge,  the  farthest  up  the  Channel,  and  at  the  greatest  distance  from 
Krakatoa  of  any  dealt  with,  shows  very  slight  disturbance  ;  but  the  undulations  are 
fairly  regular,  though  the  range  does  not  exceed  1  inch.     Period  33  minutes. 

Five  of  these  small  waves  can  be  traced  as  follows  : — 

h.     m.  h.      m.  h.      m.  h.      m.  h.      m. 

Times..  ..      1133  12  05  12  40  13  20  13  46 

Intervals        ..  32  35  40  26 

Taking  the  distance  as  10,780  miles,  the  speed  comes  out  422  miles  an  hour. 

Devonport. 

The  original  diagram  is  on  the  scale  of  0'4  of  an  inch  to  the  foot,  and  half  an 
inch  to  the  hour.  TTie  gauge  is  situated  a  long  way  up  the  harbour,  but  the  form  of 
the  land  tends  to  enlarge  the  wave. 

A  slight  oscillation  with  no  regular  period  begins  at  6  hrs.  20  mins.  on  the  28th, 
but  at  10  hrs.  43  mins.  there  is  a  stronger  wave  of  6  inches  range,  followed  by  four 
others,  with  a  mean  period  of  65  minutes.  The  intervals  are  not,  however,  very 
regular : — 

h.     m.  h.      m.  h.      m.  h.      m.  h.      m. 

Times..  ..      10  43  11  35  12  46  2  10  3  05 

m.  m.  in.  m. 

Intervals       ..  52  71  84  55 

I  take  the  10  hrs.  43  mins.  wave  as  the  one  for  comparison ;  and  the  distance 


140  CAPTAIN   WHARTON   ON   THE   SEISMIC   SEA  WAVES. 

being  11,040  miles,  10,790  of  which  are  in  deep  water,  the  speed  of  the  wave  comes 
out  at  380  miles  an  hour, 

Portland. 

The  gauge  is  on  the  inner  side  of  Portland  Breakwater ;  to  reach  which  the 
wave  has,  from  the  entrance  of  the  Channel,  to  pass  for  250  miles  over  depths  of  less 
than  100  fathoms. 

The  diagram  here  is  on  the  scale  of  1;^  inches  to  the  foot  and  1  inch  to  the  hour. 
The  indications  of  disturbance  are  not  very  conclusive,  as  no  regularity  of  period  is 
traceable  in  the  small  indentations  which  appear  on  the  28th  of  August.  They  are  so 
small  as  not  to  show  on  the  reduced  diagram,  but  they  can  be  seen  on  the  original 
from  10  hrs.  15  mins.  on  the  28th  for  some  hours.  Taking  the  earliest  appearance  at 
10  hrs.  15  mins.,  a  speed  of  406  miles  an  hour  comes  out. 

Portiamouth  and  Dover. 

The  gauges  here  show  no  sign  of  any  disturbance.  Seeing  that  the  distance  up 
the  English  Channel  in  shallow  water  is  much  greater  than  those  already  dealt  with, 
and  that  the  disturbances  at  Havre  and  Portland  are  so  very  shght,  this  is  not 
surprising. 

It  cannot  be  considered  that  the  evidence  afforded  by  any  of  these  six  gauges  in 
France  and  England  is  conclusive  ;  the  disturbance  in  all  of  them  is  too  slight.  But, 
looking  at  them  collectively,  and  seeing  the  fair  accordance  of  the  speed  of  the  waves 
— which  would  travel  on  the  same  course — the  evidence  is  strongly  in  favour  of  the 
distm'bances  on  these  gauges  being  the  effect  of  one  and  the  same  cause,  and  one 
which  originated  at  a  great  distance,  or  the  disturbance  would  have  been  of  longer 
continuance. 

Against  the  presumption  of  their  connection  with  Krakatoa  is  the  high  speed  at 
>\hich  the  wave  must  have  travelled. 

In  no  other  case  does  the  depth  corresponding  to  the  speed  come  out  otherwise 
than  under  the  probable  truth  ;  but  the  average  velocity  of  408  miles  given  by  these  six 
gauges  would  demj^nd  a  m^an  depth  of  2,500  fathoms,  whereas  it  is  very  improbable, 
from  the  known  soundings,  that  this  quantity  is  over  2,400  fathoms.  On  the  other 
hand,  the  ocean  is  deep  over  the  whole  course,  and  no  checking  of  the  velocity  would 
probably  occur  from  great  irregularities  of  the  bottom.  Though  the  wave  had  to 
round  the  Cape  of  Good  Hope,  it  would  do  so  at  a  greater  distance  than  the  wave 
which  reached  Table  Bay,  and  the  difference  between  the  speeds — viz.,  370  miles  to 
Table  Bay  and  408  as  the  average  to  the  edge  of  the  shallow  water  at  the  entrance 
of  the  English  Channel — may  be  accounted  for  in  this  way,  and  also  by  the  difficulty 
in  tracing  the  most  probable  track  for  the  wave  in  i caching  Table  Bay. 


CAPTAIN   WHARTON  ON  THE   SEISMIC   SEA  WAVES.  141 

Noth withstanding,  there  is  a  great  discrepancy  between  the  speed  from  Table 
Bay  to  the  Channel,  and  that  which  the  known  depth  should  give  by  the  formula, 
V  =  ^gh.  This  is  the  only  case  in  these  discussions  which  atFords  an  opportunity  of 
examining  the  speed  of  the  wave  in  different  parts  of  its  course.  In  no  other  in-^ 
stance  do  the  tracks  to  different  places  coincide  near  enough  to  allow  of  a  com- 
parison. 

Here  we  have  a  time  of  12^  hoiu*s  from  off  the  Cape  of  Good  Hope  to  the 
Channel,  or  a  speed  of  462  miles  an  hour.  This  corresponds  to  a  depth  of  over  3,000 
fathoms,  whereas  the  mean  depth  cannot  be  over  2,400  at  the  most,  as  estimated 
from  the  soundings,  which  are  sufficiently  numerous  to  enable  this  to  be  stated  with 
confidence. 

The  tidal  wave  is  14  hours  later  in  the  Channel  than  at  the  Cape,  which  corre- 
sponds to  a  velocity  of  412  miles  an  hour,  supposing  it  to  travel  from  one  to  the 
other.  Even  this  gives,  by  the  formula  (supposing  the  wave  to  be  "free"),  2,500 
fathoms  as  a  mean  depth,  which  is,  as  before  stated,  more  than  the  depth  known 
to  exist.  It  appears,  therefore,  either  that  the  tidal  wave  which  fiills  the  Channel 
does  not  originate  in  the  South  Indian  Ocean,  or  that  the  formula  does  not  give 
the  speed  with  sufficient  exactness. 


AUSTRALIA. 


Tidal  Diagrams  and  Eye  Observations. 

To  the  eastward  of  the  Strait  of  Sunda  the  results  are  very  meagre.  The  few 
tide  gauges  in  Australia  are  badly  placed,  up  estuaries,  and,  with  one  exception,  show 
very  slight  and  irregular  disturbances. 

In  New  Zealand  two  automatic  gauges  are  at  work,  but  the  one  at  Port  Lyttel- 
ton,  which  alone  shows  much  disturbance,  is  difficult  to  interpret ;  and,  moreover,  the 
waves  it  has  registered,  as  well  as  the  reports  of  .eye-witnesses,  tend  to  show  that  the 
waves  felt  in  New  Zealand  had  some  other  point  or  points  of  origin  than  the  Strait  of 
Sunda.  The  disturbances  marked  on  the  three  gauges  at  the  Sandwich  Islands, 
Alaska,  and  San  Francisco  are,  as  will  be  seen,  also  apparently  unconnected  with 
Krakatoa. 

West  Australia. 

Here  there  are  no  tide  gauges ;  and,  as  the  reports  are  veiy  crude  and  vague, 
not  much  reliance  can  be  placed  upon  them. 

U 


142  CAPTAIN  WHAETON  ON  THE  SEISMIC   SEA  WAVES. 

Cossack^  W.  Australia. 

At  4.30  p.m.  on  the  27th  an  extraordinary  tide  is  said  to  have  set  in,  which  rose 
nearly  5  feet,  then  went  out  just  98  rapidly,  the  coming  in  and  going  out  not  occupy- 
ing more  than  SO  minutes. 

This  time  gives  a  speed  of  423  miles  an  hour  for  the  995  miles  from  the  Strait  of 
Sunda  to  the  190  fathoms  off  Cossack.  This  gives  a  depth  of  2,600  fathoms — 
probably  near  the  truth, 

Geraldton,  W,  Australia. 

Here  the  water  is  stated  to  have  suddenly  risen  6  feet  at  8  p.mu  on  the  27th, 
and  receded  sa  far  that  boats  anchored  in  6  feet  water  were  left  high  and  dry.  It 
rose  again,  but  not  so  high  as  at  first,  and  continued  rising  and  fidling,  gradually 
getting  less  and  less  till  about  noon  the  next  day,  when  it  ceased. 

If  this  time  be  taken,  it  would  give  a  speed  of  only  170  miles  an  hour  from 
the  Strait  of  Sunda.  As  at  this  time  it  had  been  dark  for  two  hours,  it  may  be 
regarded  as  doubtful  whether  the  wave  remarked  at  8  o'clock  was  really  the  first  that 
reached  Geraldton. 

From  the  rapid  rise  mentioned^  it  appears  that  these  waves  were  short  ones  at 
both  Cossack  and  GeraldtoOi 

Porl  Adelaide,  S.  Australia. 

The  diagram  here  shows  disturbance,  but  of  so  irregular  a  character  that 
nothing  can  be  founded  upon  it. 

The  gauge  is  placed  inside  a  bar,  and  some  miles  up  the  river. 

WUliamistoumf  Victoria. 

This  bay  is  situated  near  the  head  of  Port  Phillip.  The  wave  coming  from  sea- 
ward would  have  to  pass  ovet  30  iniles  of  shallow  water  after  getting  through  the 
narrows  at  the  entrance,  where  the  tides  are  very  strong.  Nevertheless,  there  is  a 
marked  disturbance,  which  commences  at  4  hrs.  30  mins.  on  the  28th,  the  range  being 
only  4  inches.  This  lasts  until  the  31st,  but  can  be  followed  as  a  regular  series  for 
only  twenty-seven  waves.  The  mean  period  is  86  minutes,  but  it  varies  considerably. 
There  is  only  one  series  of  waves. 

A.   in*  A.    m.  A.    m»  a.    m.  a.     al  a.     ia. 

Times     , .      4  40  6  40  8  08  9  35  10  55  12  10 

H.   m.  h.   Ai.  h.    m.  h..    m.  a.  'm.  a.    m. 

Intervals  2  00  1  28  1  27  1  20  1   15  1  30 


CAPTAIN  WHAETON  ON  THE  SEISMIC    SEA  WAVES.  143 

ii«   ID*  h*    nL  Om    nia  D.   in.  n.     hl.  a.     in. 

Times  ..  13  40    15  10    16  35    17  50     19  05     20  10 

h.    m.  h.    m.  h.    m.  h,    m.  h.    m.  h:     m. 

Intervals  1  30  1  25  1   15  1   15  1  05  1  30 

Times     ..    21  40         23  25  1  05  2  08  3  35  5  00 

Intervals  1  45  1  40  1  03  1  27  1  25  1  45 

Times     ..      6  45  7  45  9  25         11  00  12  00  13  42 

Intervals  1  00  1  40  1  35  1  00  1  42  1  23 

Times     ..    15  05         16  20         17  27         19  25 
Intervals  I  15  1  07  1  58 

The  distance,  measured  from  the  1000-fi^thom  line  from  off  the  Strait  of  Sunda 
to  the  130  fathoms  off  the  entrance  to  Bass  Strait  is  3,130  miles.  The  4  hrs.  40 
mina  wave  gives  a  speed  of  232  miles  an  hour,  which  corresponds  to  a  depth  of  800 
fathom&  The  very  few  soundings  which  exist  on  or  near  this  route  are  all  more 
than  2,000  fathoms,  from  which  it  appears  that  if  the  distiurhance  is  connected  with 
Krakatoa  the  earlier  waves  must  have  been  so  small  that  they  were  not  recorded  on 
the  gauge.  The  length  of  the  waves  precludes  the  supposition  of  any  local  cause 
or  undulations  caused  by  gales.  The  original  diagram  is  on  a  scale  of  1  inch  to 
the  hour. 

Sydney,  New  South  Wales. 

The  record  at  this  port  is  disturbed,  but  merely  at  high  water,  and  no  deduction 
from  it  appears  possible. 

On  the  subject  of  the  Sydney  gauge,  Mr.  H.  C.  Bubbell,  F.II.S.,  the  Government 
Astronomer  of  New  South  Wales,  writes  as  follows  :  — 

"  I  should  teU  you  that  there  is  always  a  little  unsteadiness  in  the  Sydney  tidal 
'wave  at  high  water,  and  when  the  so-called  earthquake  waves  do  reach  oxu:  coast,  as 
they  fr^uently  do,  they  are  always  greatest  about  the  time  of  high  water. 

"  Two  reasons  for  the  irregular  high-water  curve  have  been  offered — 1st,  that, 
when  the  tide  wave  rushes  into  the  complex  ^stem  of  bays  forming  Sydney  Harbour, 
extending  20  miles  in  one  direction  and  nearly  as  much  in  two  others,  the  water 
oscillates  till  it  comes  to  its  level ;  and  2ndly,  and  more  probably,  that  the  tide  wave 
is  divided  by  New  Zealand,  and  that  the  two  branches  arrive  on  this  coast  at  different 
times. 

"I  mention  this  so  that  you  may  make  allowance  for  it  in  estimating  the 
disturbances  recorded  at  high  water, 

*'  Again,  the  common  so-called  earthquake  waves  are  fairly  regular  in  interval, 
from  crest  to  crest,  being  25  minutes  to  30  minutes,  while  the  best  marked  of  those  I 
send  you  have  a  much  longer  intervali  about  45  minutes. 

u  2 


144  CAPTAIN  WHARTON  ON  THE  SEISMIC  SEA  WAVES. 

"  As  soon  as  we  heard  of  the  great  eruption  at  Krakatoa  I  tried  to  connect  our 
recorded  waves  with  it,  but  I  found  that  the  velocity  for  one  set  was  too  great,  and 
for  the  other,  too  small. 

"  I  did  not  hear  any  explosions  on  August  27th,  nor  did  I  hear  of  anyone  who 
heard  such  noises  at  that  time/' 


NEW  ZEALAND. 


Tidal  Diagrams  and  Eye  Observations. 

From  New  Zealand  has  been  received  a  report  from  Dr.  Hector,  F.R.S.,  accom- 
panied by  two  tidal  diagrams  from  Port  Lyttelton  and  Dunedin  respectively.  The 
report  gives  the  eye  observations  at  different  places.  From  this  it  appears  that  at 
10  spots  on  the  coast,  disturbance  was  noticed  on  various  dates  between  the  28th  of 
August  and  the  1st  of  September. 

I  opine  that  none  of  these  could  have  originated  from  the  Strait  of  Sunda,  the 
interval  elapsing  between  the  great  wave  there  and  the  earliest  disturbance  in  New 
Zealand  being  far  too  great  to  permit  the  supposition  that  that  wave  could  have 
caused  them.     It  was  at  Port  Lyttelton,  by  Dr.  Hector's  report,  that  the  dis 
turbance  was  finst  noticed. 

Port  LytteltoUy  New  Zealand. 

The  tidal  diagram  here  is  on  a  large  scale,  2  inches  to  the  foot  and  1  inch  to 
the  hour. 

The  curve  is  most  irregular,  and  unfortunately  at  the  time  Dr.  Hector  mentions 
as  that  at  which  the  disturbance  commenced,  the  chain  was  entangled. 

It  is  difficult  to  arrive  at  any  conclusion  as  to  the  exact  nature  of  the  disturbance, 
from  the  absence  of  diagrams  of  any  days  when  the  movement  was  normal.  On  all 
other  days  for  which  diagrams  are  given,  from  the  28th  of  August  to  the  3rd  of 
September,  abnormal  motion  appeai-s  to  be  taking  place. 

This  is  of  two  kinds ;  small  oscillations  with  an  average  of  about  ten  minutes, 
but  with  much  variation,  and  larger  and  very  irregular  rises  and  falls. 

This  is  quite  unlike  the  diagrams  from  other  parts  to  the  west  of  Sunda  Strait, 
where  the  disturbance  may  be  considered  as  undoubtedly  due  to  Krakatoa.  No 
regulax  period  can  be  recognised,  and  no  result  is  obtainable. 

Taking  Dr.  Hector's  statement  that  the  tide  ebbed  and  flowed  in  an  exceptional 
manner  on  the  evenmg  of  the  28th,  in  conjunction  with  the  broken  record  of  the 


CAPTAIN  WHARTON   ON  THE  SEISMIC   SEA  WAVES.  145 

gauge  at  that  time,  9. 45  p.m.  may  be  considered  as  about  the  hour  when  the   first 
wave  crest  reached  the  port. 

This  gives,  for  the  distance  from  Krakatoa,  which,  eliminating  the  shallow  water 
as  before,  is  4,772  miles  from  the  1,000  fathoms  off  Sunda  Strait  to  the  100  fathoms 
off  Port  Lyttelton,  159  miles  an  hour;  which  corresponds  to  a  depth  of  377  fathoms. 
The  true  depth  is  probably  not  less  than  2,300  fathoms. 


Dunediuy  New  Zealand. 

This  gauge  is  situated  at  the  head  of  the  long  Bay  of  Otago.  It  shows  a  disturb- 
ance merely  at  high  water  on  the  29th  at  3  p.m. 

Dr.  Hector  states  that  at  Port  Chalmers,  four  miles  lower  down  the  harbour, 
the  water  rose  and  fell  irregularly  from  11.30  a.m.  to  3  p.m.  on  the  29th. . 

Taking  11.30  as  the  earliest  time,  the  wave  would  have  taken  45  hrs.  9  mins.  to 
travel  from  Krakatoa,  which  gives  a  speed  of  102  miles  an  hour  for  the  4,536  miles 
from  Sunda  Strait  to  the  500  fathoms  off  Otago.  This  corresponds  to  a  depth  of 
150  fathoms,  the  true  depth  being  probably  not  less  than  2,300  fathoms. 

At  other  places  in  New  Zealand  the  discrepancy  is  the  same,  or  even  greater. 

Thus  Dr.  Hector  states,  that  at  Timaru,  "a  wave  was  experienced  several 
times,  and  a  very  marked  disturbance  of  the  water  occurred  on  the  morning  of 
the  29th." 

"  At  Nelson,  at  8  p.m.  on  September  the  Ist,  the  tide  suddenly  rose  to  some 
distance  above  high  water-mark,  the  time  for  high  water  not  being  tiU  after  9  p.m. 
It  fell  again  about  10  inches,  after  which  it  commenced  to  flow  as  usual." 

"  At  Thames,  at  8.15  a.m.  on  the  30th  of  August,  the  tide,  which  had  previously 
been  ebbing,  suddenly  turned  to  flood,  running  past  the  lighthouse  at  Passage  like  a 
mill  race  for  about  half  an  hour.  It  then  just  as  suddeiJy  turned  to  ebb  again,  about 
two  hoiu^  being  wanted  to  low  water.  The  disturbance  was  still  noticed  at  the 
Thames  on  August  the  31st." 

"  At  Auckland  a  tidal  wave  was  experienced  just  before  the  last  of  the  ebb  tide 
on  August  the  29th.     The  rise  was  about  6  feet." 

"  At  Russell,  Bay  of  Islands,  and  at  Mongonui,  tidal  disturbances  were  noticed 
several  times  in  rapid  succession  on  August  the  29th." 

"  On  August  the  29th  earthijuake  shocks  were  felt  at  Brisbane,  Bockhampton, 
and  Gladstone  in  Queensland  ;  also  at  Patea  in  Taranaki  District,  New  Zealand-" 

"  At  midnight,  August  29th — 30th,  a  severe  shock  was  felt  at  Kiana,  New  South 
Wales,  about  90  miles  south  of  Sydney." 

"  On  August  the  31st  a  slight  shock  was  felt  in  South  Australia." 

Dr.  Hector  adds,  after  expressing  his  opinion  that  the  tidal  disturbances  were 
probably  due  to  Krakatoa,  and  referring  to  the  great  earthquake  at  Arica  in  1868 : — 


146  CAPTAIN  WHARTON  ON  THE  SEISMIC  SEA  WAVBa 

^'  On  both  occasions  we  had  slight  earthquake  shocks,  produced  probably  as  a 
secondary  result  from  the  inequality  of  pressure,  but  similar  slight  shocks  are  not 
infrequent,  without  being  accompanied  by  tidal  disturbances." 

It  will,  I  think,  be  evident  that  no  wave  that  occurred  more  than  15  hours 
(equivalent  to  a  mean  depth  of  1,300  fathoms)  after  the  eruption  at  Erakatoa  could 
be,  under  any  hypothesis,  attributed  to  it ;  whereas  the  earliest  of  the  disturbances 
here  recorded  took  place  48  hours,  and  the  latest  116  hours,  after  the  10  o'clock  wave 
left  Exakatoa. 

The  diversity  o£  times  recorded  in  different  places  in  New  Zealand,  as  well  as  the 
brief  duration  of  aome  of  the  disturbances,  seem  to  point  to  some  local  cause ;  and  it 
appears  that  the  earthquakes  mentioned  by  Dr.  HsorOB  are  far  more  likely  to  have 
caused  them  than  is  the  disturbance  in  the  Strait  of  Sunda  on  August  the  27th. 
I  think  that  that  gentleman  will  probably  agree  in  this  conclusion  when  he  sees 
the  evidence. 


THE  PACIFia 


Tidal  Diagrams  and  Eye  OnsEBVATioiNs. 

We  have  diagranus  from  three  places  in  the  Pacific,  viz.,  Honolulu ;  St.  Pauls, 
Eodiak ;  and  Saucelito,  near  San  Francisco. 

These  all  show  disturbance,  but  I  do  not  think  that  it  can  be  considered  to  have 
any  distinct  connection  with  the  eruption  in  Sunda  Strait^  as  the  speed  of  the  waves 
deduced  is  in  all  cases  too  high  for  probability ;  nor  do  the  differences  of  times  of 
arrival  at  the  three  stations  agree  with  requirements  of  distance  by  the  several 
tracks^ 

At  the  first  glance  at  a  chart  it  seems  that  the  undulations  to  these  stations 
might  have  ti^velled  throi^h  the  cl\annels  of  the  Eastern  Archipdago,  and  thus  have 
gained  the  Psunfic ;  but  a  dose  investigation  will  show  that  this  is  impossible.  The 
most  direct  route  is  vid  the  Java  and  Mores  Sea  and  the  lltolucca  passag6i,  and  north 
of  New  Guinea*  We  have  already  seen,  however,  that  the  wavQ  travelling  to  Ujong 
Pan^ia— which  is  om  this  route — required  10^  hours  to  traverse  the  distance,  which 
is  440  miles.  BeyondUjong  Pangka  is  another  200  miles  of  water  of  about  40  fikthoms 
before  the  deeper  watw  of  the  Flores  Sea  is  reached.  This  would  take  another 
4  hours,  making  14^  hours  before  the  wave  was  in  deep  water,  and  it  would  still  have 
5,400  nules  to  travel  before  reaching  Honolulu.  As  the  first  large  wave  is  recorded 
on  the  Honolulu  diagram  only  11  hours  after  the  great  wave  left  Eiakatoa,  it  is 
obvious  that  it  had  not  time  to  proceed  by  this  route. 

By  the  south  of  Java  and  vid  Torres  Straits,  we  meet  with  the  same  di£Giculty, 


CAPTAIN  WHARTON  ON  THE  SEISMIC  SEA  WAVES.  147 

as,  in  parsing  the  latter,  a  distance  of  over  700  miles  of  water  averaging  30  fathoms 
in  depth,  must  be  traversed. 

The  waves  must  therefore  have  passed  south  of  Tasmania. 

Honolulu. 

This  diagram,  on  a  scale  of  1*7  inches  to  the  foot  and  0*9  inch  to  the  hour, 
shows  a  slight  disturbance  commencing  at  17  hours  of  the  26th.  At  3  hrs.  20  mins. 
of  the  27th  a  larger  disturbance  commenced,  and  lasted,  with  gradually  diminishing 
height,  until  September  the  1st — a  period  of  five  days.  This,  then,  is  unlike  any 
of  the  other  diagrams.  The  maximum  wave  is  about  5  inches.  The  waves  are 
comparatively  short — ^averaging  about  30  minutes.  Taking  the  3  hrs.  20  mins. 
wave,  we  find,  for  the  distance  of  8,326  miles,  a  speed  of  nearly  800  miles  an 
hour,  which  requires  a  depth  of  9,500  fathoms,  the  actual  depth  being  probably 
not  above  2,300  fathoms. 

St  PauFsy  Kodiak,  Alaska. 

This  diagram,  on  a  scale  of  0*9  inch  to  the  foot  and  0*75  inch  to  the  hour, 
shows  disturbance  from  8  hours  of  the  27th  of  August.  A  larger  wave  is  recorded 
at  16  hrs.  45  min&,  and  the  disturbance  is  marked  to  the  end  of  the  30th.  The 
waves  are  short  and  irregular,  and  the  greatest  wave  is  3  inches.  Taking  the 
16  hrs.  45  mins.  wave,  the  speed  for  the  distance  of  10,190  miles  comes  out  459  miles 
an  hour,  which  corresponds  to  a  mean  depth  of  3,100  fiithoma  This  is  too  much,  but 
not  so  startling  as  the  Honolulu  result,  with  which  it  fails  to  agree  in  any  way. 

Saticelito,  San  Francisco* 

This  diagram,  on  a  scale  of  1  inch  to  the  foot  and  0*45  inch  to  the  hour,  shows 
disturbance  from  7  hours  on  the  27th.  The  first  large  wave  is  at  13  hrs.  20  mins., 
and  is  followed  for  7  hours  by  others,  when  they  diminish  to  a  small  and  irregular 
oscillation,  which  lasts  until  the  30th  of  August.  The  13  hrs.  20  mins.  wave  is 
6  inches  in  height.  Taking  this  wave,  we  find  for  the  distance  of  10,343  miles  a  speed 
of  594  miles  an  hour,  which  requires  a  depth  of  5,000  fathoms. 

It  wiU  be  observed  that  none  of  these  speeds  agree,  either  with  one  another 
or  with  the  known  facts  and  probabilities  of  the  depths. 

Nor  is  it  possible  to  localise  any  one  centre  from  which  these  disturbances  could 
have  simultaneously  originated,  so  that  the  times  of  arrival  at  the  three  gauges  will 
agree. 

An  earthquake  occurring  near  the  Sandwich  Islands  or  to  the  south-west  of 
them  would  give  rise  to  waves  which  would  reach  Honolulu  and  San  Francisco  at 
times  agreeing  with  the  recorded  differences  of  arrival  at  these  places  ;  but  it  would 
be  at  St.  Paul's  six  hours  earlier  than  the  registered  time. 


148  CAPTAIN  WHARTON  ON  THE  SEISMIC  SEA  WAVES. 

Any  other  assumed  position  would  make  the  discrepancy  greater.  Either  the 
waves  chosen  for  comparison  on  the  three  diagrams  are  not  identical,  nor  nearly  so, 
or  the  disturbances  are  not  due  to  the  same  cause. 


MAIN  CONCLUSIONS. 


LUGt 


kfin 


1-59 


The  main  conclusions  at  which  I  arrive  may  be  summed  up  as  follows  : — 

1.  That  the  sea  disturbance  was  probably  composed  of  two  descriptions  of  waves, 

long  waves  with  periods  of  over  an  hour,  and  shorter  but  higher  waves  with 
irregular  and  much  briefer  intervals. 

2.  That   the    greatest    disturbance,   probably   foimed   of   both   descriptions   of 

waves,  originated  at  Krakatoa  at  about  10  a.m.,  local  time,  on  the 
27th  of  August,  and  was,  on  the  shores  of  the  Strait  of  Sunda,  about 
50  feet  high.  rot 

3.  That  the  long  waves  of  this  disturbance,  of  an  original  period  of  about  two 

hours,  were  alone  marked  by  the  automatic  gauges. 

4.  That  the  speed  of  the  two  descriptions  of  waves  was  about  the  same. 

5.  That  the  speed  of  those  waves  that  can  be  fairly  identified,  measured  by  the 

time  of  arrival  of  the  first  large  wave,  and  counting  from  the  10  a.m.  wave 
at  Krakatoa,  was  in  all  cases  less  than  the  depth  of  water  would  demand 
according  to  theory  ;  assuming  that  the  waves  taken  for  comparison  were 
identical  with  the  10  o'clock  wave  from  Krakatoa. 

6.  That  the  first  large  wave  recorded  on  the  gauges  was  in  most  cases  preceded 

by  smaller  undulations,  which  did  not,  however,  accord  with  the  period  of 
the  Larger  waves. 

7.  That   to   the   north    and    east    in    the    Java    Sea    the  long  wave    can   be 

traced  for  450  miles,  but  it  was  at  this  distance  reduced  to  a  very  small 
undulation. 

8.  That  to  the  west  the  longwave  travelled  over  great  distances;  reaching  Cape 

Horn  and  possibly  the  English  Channel. 

9.  That  the  shorter  waves  reached  Ceylon  and  perhaps  Mauritius, 

10.  That  to  the  south  and  east  of  Sunda  Strait  the  propagation  of  the  dis- 
turbance was  limited ;  probably  not  extending  beyond  the  west  coast  of 
Australia. 

11.  That  the  disturbances,  noted  both  by  eye  observers  and  by  the  gauges  in 

New  Zealand  and  in  the  Pacific,  had  no  connection  with  Krakatoa,  but  were 
the  results  of  other  seismic  action,  and  were  apparently  due  to  more  than 
one  centre  of  movement. 


lUGUST     26th— 30th,      1883. 


'^J 


Fink  Onat  WaTe. 

lesin 
ihoal 

Tine  of  Ware 
in  known  tboBl 
depth!  by  Airy. 

Outer 
depth. 

Dirtuoei 

in 
MidOoeui. 

Time  of 
Max.  Dii- 
tarbance 
after  Pint 
Great 

H^^ht 

Max. 

Ware 
in 

Time  in 

Speed  in 
Mid  Ocean. 

D 

Mid  Ocean. 

Ware. 

inches. 

Miles  per 

b.    m. 

Fathomt. 

h.    m. 

bour. 

] 

rest 

0    16 

1000 

, , 

•  • 

•  • 

•  • 

•  • 

Mt 

2    80 

, , 

0 

0    0 

0 

0 

72 

1 

10    46 

, , 

0 

0    0 

0 

P 

10 

1 

12    22 

•  • 

0 

0    0 

0 

P 

7 

1 

18    18 

«• 

0 

0    0 

0 

P 

•  • 

lfti|f-fnTif^lP'n«^ 

-69 

17+16-88 

60 

481 

8  18 

186 

P 

•  • 

-72 

26  +  16-41 

1000 

1608 

4*16 

878 

•• 

•  • 

-78 

80+16-46 

600 

1687 

6  27 

812 

, , 

, , 

-80 

48  +  16-64 

160 

1806 

6  18 

867 

1  14 

12 

-72 

27  +  16-48 

100 

1868 

6  81 

838 

0    0 

4 

-02 

56+16-72 

100 

1909 

6  89 

888 

0    0 

6 

-77 

64+16-80 

28 

2008 

6  81 

808 

1  30 

12 

-160 

190  +  16-206 
h.    m. 

160 

2000 

640 

861 

0    0 

8 

I 

2    00 

Same 

Wave. 

, , 

, , 

, , 

8 

1 

1    46 

Same 

Wave. 

•  • 

•  • 

, , 

4 

\ 

mng.mDt.miit. 

•Hp^uo 

68  +  16-84 

1000 

2090 

624 

826 

12    0 

14 

i.67 

6+16-22 

lOOf 

1660 

4  46 

847 

-  •  • 

•  • 

'^17 

192  +  16-206 

lOOOP 

2482 

788 

881 

060 

7 

X 

124+16-140 

lOOOP 

8082 

8  64 

840 

180 

16 

64+16-80 

1000 

8642 

10  81 

847 

080 

6 

' 

No 

* 

-^ 

9  +  16-26 

800 

2619 

648 

876 

infonna- 

» •  • 

tion. 

86+16-61 

40 

2662 

7  12 

870 

do. 

•  • 

8  +  16-24 

1000 

2848 

7  08 

408 

do. 

, , 

82  +  16-98 

200 

2876 

7  42 

878 

do. 

, , 

24  +  16-40 

1000 

4660 

11  44 

888 

6  00 

19 

^     82  +  16-48 
^  48  +  16-69 

1000 
1000 

4611 -f 
6001 

12  24 
14  24 
18  81 

871 
820 
870 

800 
1  00 
1  00 

J80 
14 

"•^ 

^^ 

mm 

^  '4 


u 


mxer 


horns 

100 
200J 


000 

Km 

ooo 

000 


190 
.  100 

130 


500 
4Q 


250 

100 
000 


tUGUST      26th— 30th,      1883. 


>uter 
epth. 


homB. 


Inks' 


POM 


100 


OOU^ 
000 

P0B3-- 
DOT]-- 


Cow^QO 

SYDJ- 
POK  40 


H0ir»2BO 
ST.  plOO 

ON 


Flnt  Oreat  Ware. 


DifUmces 

in 
mdOoMn. 


6619 

7411 
7709 

11887 


996 
1890 

8180 


4686 
4772 


Time  in 
MidOoMUL 


10190 
10848 


h.  m. 

18  84 

24  61 

29  12 

22  12 


18    11 


10729 

25 

18 

10724 

26 

58 

10790 

28 

27 

10780 

25 

40 

10780 

26 

27 

10780 

26 

29 

2    21 
8    08 

18**29 


44    06 
29    64 


,10  26 
22  11 
17    28 


Speed  in 
MldOoi 


Ocean. 


Miles  per 
hour. 


487 


261 

847 


426 
414 
880 
418 
406 
422 


428 
170 


108 
169 


797 
469 
694 


Time  of 
Mftz.  Dia- 
turbance 
after  Fint 
Qraat  Ware. 


11.  m. 

12  00 

1  00 

1  00 


12    00 
6    00 

2 'OO 

? 
0    88 


Max. 

Ware 

in 


Dnratian 

of 

Disturbance. 


Hours. 


over  60/ 
I 

„    46{ 


26 
6 

9 

doubtful 

? 

2i 


? 
16 

92 


182 

88 
88 


Dept 
indica 

Formi 


850( 
106( 

94( 
178( 


580( 


262( 
205( 
264( 
242( 
264( 


264( 
800 


16C 
87€ 


940C 
8116 
6180 


CAPTAIN  WHAETON  ON  THE  SEISMIC  SEA  WAVES. 


149 


12.  That  from  the  great  differences,  caused  perhaps  by  local  circumstances,  in  the 
appearance  of  the  disturbance  on  the  various  tidal  diagrams,  no  precise  or 
close  comparison  between  them  can  be  made,  and  this  doubt  of  the  identifi- 
cation of  any  particular  wave  at  different  places,  causes  much  uncertainty 
in  the  result,  as  far  as  it  relates  to  the  speed  of  the  waves. 

It  may  be  remarked  that,  with  regard  to  conclusion  No.  5,  Professor  Milne,  in 
his  recent  work  '  On  Earthquakes,'  finds  the  same  for  such  other  sea  waves  as  have 
been  traced  for  long  distances  across  the  Pacific ;  though  the  point  of  genesis  has 
never  been  so  certainly  known  as  in  this  instance. 


Speed  of  Free  WaveSy  by  Sir  George  Any. 


Depth  in 

Depth  in 

Geogi-aphical 

Depth  in 

Depth  in 

Geographical 

feet 

fathoms. 

miles  per  hour. 

feet. 

fathoms. 

miles  per  hour. 

3 

0-6 

5-8 

1,998 

333 

150 

6 

1 

8-2 

2,400 

400 

164 

12 

2 

11-6 

3,o:o 

500 

184 

18 

3 

14-2 

3,600 

600 

201 

30 

5 

18-4 

3,996 

666 

212 

42 

7 

21-0 

4,200 

700 

217 

60 

10 

26-1 

4,800 

800 

233 

78 

13 

30-0 

5,400 

900 

247 

90 

15 

31-9 

6,000 

1,000 

260 

102 

17 

33-9 

7,500 

1,250 

291 

120 

20 

36  8 

9,000 

1,500 

318 

150 

25 

41-0 

10,500 

1,750 

344 

180 

30 

44*0 

12,000 

2,000 

367 

198 

33 

46-0 

13,500 

2,250 

390 

•          240 

40 

50-3 

15,000 

2,500 

411 

300 

50 

56-5 

16,500 

2,750 

432 

360 

60 

63-8 

18,000 

3,000 

451 

420 

70 

68-9 

19,500 

3,250 

469 

•    480 

80- 

73-7 

21,000 

3,500 

487 

600 

100 

82-3 

22,500 

3,760 

504 

798 

133 

94-9 

24,000 

4,000 

520 

900 

150 

101 

25,500 

4,250 

6.36 

996 

166 

106 

27,000 

4,500 

552 

1,200 

200 

116 

28,500 

4,750 

567 

1,800 

300 

142 

30,000 

5,000 

591 

X 


150 


CAPTAIN  WHAETON  ON  THE   SEISMIC  SEA  WAVES. 


List  of  Tidal  Diagrams. 


PlATB 

PUTB 

1 .  Tandjong  Priok  (Batavi. 

a)        XVII. 

19. 

Table  Bay 

XXIL 

2.  Ujong  Pangka  . . 

.       XVIII. 

20. 

Moltke  Harbour 

<• . 

XXIII. 

3.  Ujong  Sourabaya 

.       XVIII. 

21. 

Orange  Bay 

XXIII. 

4.  Rarang  Eleta    . . 

.       XVIII. 

22. 

Colon 

*  • 

XXIII. 

5.  Port  Blair 

XTX. 

23. 

Socoa     . . 

« . 

XXIV. 

6.  Negapatam 

XIX. 

24. 

Rochefort 

•  • 

XXV. 

7.  Madras   . . 

XIX. 

25. 

Devonport 

•  • 

XXVL 

8.  Vizagapatam 

XIX. 

26. 

Cherbourg     •    . . 

•  • 

XXVIL 

9.  False  Point 

XIX 

27. 

Portland 

•  • 

XXVL 

10.  Dublat 

XX. 

28. 

Havre    . . 

*  • 

XXVIIL 

11,  Diamond  Harbour 

XX. 

•29. 

Port  Adelaide  . . 

*  • 

XXIX. 

12.  Kidderpore  (Calcutta)  . 

XX. 

30. 

Williamstown,  Port 

Phillip 

XXIX 

13.  Beypore  . . 

XXI. 

31. 

Sydney  . . 

•  • 

XXIX. 

14.  Bombay  . .          . .          , 

XXI. 

32. 

Lyttelton 

•  • 

XXX. 

15.  Kurrachee 

XXI. 

33. 

Honolulu 

•  • 

XXX. 

16.  Aden 

XXII. 

34. 

SK  Paul,  Kodiak 

•  « 

XXXL 

17.  Port  Alfred        ..          . 

XXII. 

35. 

Saucelito,  San  Francbco 

XXX  r. 

18.  Port  Elizabeth  .. 

XXII. 
Illustratr 

Flxtr 

^eCht 

irts. 

Platb 

1 .  Sunda  Strait,  before  erupi 

bion    XXXII. 

3. 

Java  Sea           . . 

•  « 

XXXI V, 

2.  Sunda  Strait,  after  erupti 

on    XXXIII. 

4.  Wprld   .. 

•  • 

XXXV, 

•^ 


W.  J.  L.  Whaeton. 


PlaJUXm 


0        Noon        14 

« 

18 

20 

22 

Mid 

\ 

; 

4- 

i 

> 

\ 

1 

Auff.30^ 

0        Noon        M- 

16 

18 

20 

22 

Mm 

~1 

!  i 

I 

1 

1 

1 

1 

! 

i 
i 

! 

f^ 

\ 

z' 

i^S/V 

X 

^^ 

'^ 

^ 

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A 

y 

^ 

AX' 

V 

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r^^ 

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r? 

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15 

wv 


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12 

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K) 
9 
8 

7 
G 
5 
4 
3 
2 
I 


Malby  &  Sons,  T.ith  . 


S      MM 


iiat^  xvm. 


22         Mid        2         4  6  8         10       Noon      14l6»2022Mid24  6  8         10 


^Ia2"by  &  Sons,  lith.. 


^-^'^-l-ntoa.  Hep.  Roy.  Soc.  Cr"-- 
Md       2  4 


LOCAL        CIVIL      TIME 


6  8  10        Noon        14  16  18  20  22        Mid  2  4  6  8 


JOC. 


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PART   lY. 


ON  THE  UNUSUAL  OPTICAL  PHENOMENA  OF  THE  ATMOSPHERE, 
1883-1886,  INCLUDING  TWILIGHT  EFFECTS,  CORONAL  APPEAR- 
ANCES, SKY  HAZE,  COLOURED  SUNS,  MOONS,  &C. 

By  ike  Hon.  F.  A.  Rollo  Russell  and  Mr.  E.  Douglas  Archibald.* 


As  this  part  is  necessarily  very  long,  we  have  found  it  convenient  to  divide  it 
into  sections  and  sub-sections;  though  even  thereby  a  fresh  difficulty  and  some 
repetition  are  introduced  in  consequence  of  the  intimate  relation  subsisting  between 
the  various  phenomena.  We  have,  however,  finally  decided  upon  the  following 
arrangement : — 

Section  I. — 

(a.)  Descriptions  of  the  unusual  twilight  glows  in  various  parts  of  the  world, 
in  1883-4. 

(b.)  Proximate  physical  cause  of  the  unusual  twilight  glows. 

(c.)  The  blue,  green,  and  other  coloured  appearances  of  the  sun  and  moon. 

(d.)  The  sky  haze  and  some  of  its  effects. 

(e.)  The  large  corona  round  the  sun  and  moon,  generally  known  as  "  Bishop's 
Ring." 

Section  II. — General  list  of  dates  of  first  appearance  of  all  the  optical  pheno- 
mena (with  maps  representing  the  distribution). 

*  The  authorship  of  the  sections  and  sub-sections  is  indicated  bj  the  name  appended  to  each. 

X  2 


152  THE  HON.  ROLLO  RUSSELL 

Section  IIL — 

(a.)  General  geographical  distribution  of  all  the  optical  phenomena  in  space 
and  time ;  including  also  velocity  of  translation  of  '*  smoke  stream," 

(b.)  Connection  between  the  propagation  of  the  sky  haze  and  its  accompanying 
optical  phenomena  and  the  general  circulation  of  the  atmosphere. 

(c.)  Spread  of  the  phenomena  round  the  world. 

Section  IV. — Diurnal  and  secular  variation  in  the  duration  and  brilliancy  of  the 
twilight  glows,  and  the  height  above  the  earth  of  the  stratum  which 
caused  them. 

Section  V. — ^Previous  analogous  glow  phenomena,  and  corresponding  eruptions. 

Section  VI. — Individual  opinions  expressed^  and  hypotheses  suggested,  to  account 
for  the  abnormal  optical  phenomena. 

Section  VII. — General  analysis  of  the  connection  between  the  unusual  meteoro- 
logical phenomena  of  1883-86,  and  the  eruptions  of  Erakatoa  in  May  and 
August,  1883. 


PART    IV.— SECTION  I.   (a). 

Descriptions   of  the  Unusual  Twilight   Glows  in  Various  Parts  of  the 

World  in  1883-84. 

By  the  Hon.  Rollo  Russell. 


introduction. 

The  Committeb  has  been  favoured  with  voluminous  correspondence,  all  which  has 
received  careful  consideration,  and  much  has  been  utilized  in  various  sections  of  this 
Part,  but  only  a  small  portion  could  be  quoted  in  extenso.  The  following  descrip- 
tions have  been  selected,  partly  from  it  and  partly  from  printed  sources,  as  indicative 
of  the  nature  of  the  phenomena  in  various  countries,  and  are  arranged  chronologically. 


ON  THE  UNUSUAL  TWILIGHT  GLOWS. 
List    op    Obseevers. 


I5d 


Bishop,  Rev.  S.  E. 
Haboraye,  Mr.  L. . . 
:Manlet,  Rev.  W.  R. 
Parkbb,  Mr.  H.,  F.R.  Met. 
Mbldbum,  Dr.  C,  F.R.S 
Todd,  Mr 


Anon 

Gebbeb,  Dr.  A. 
Tebbott,  Mr.,  F.R.A.S 
Meteb,  HeiT  G.     . . 
Russell,  The  Hon.  Rollo, 
Stoddabd,  Prof.  0.  N. 


Soc. 


F.R. 


Met.  Soc. 


Divbbs,  Prof.  E. 
Baadsb,  Herr  J. 
DupouB,  M. 


Capello,  Captain  de  Brito 
Helmholtz,  Prof,  von 
Hopkins,  Mr.  Gerabd 
Paschwitz,  Dr.  E.  von  R. 
Latabd,  Mr.  E.  L. .  • 
MoNTESSUS,  M.  de . . 
Ballot,  Mr.  John  . . 


Pelaqaud,  M. 
Bezold,  Prof,  von . 


Honolulu 

Sydney,  N.S.W 

Ongole,  Southern  India 

Ceylon  . . 

Mauritius 

Adelaide   Observatory,  South 

Australia    . . 
Magdeburg 
Gluckstadt 

Windsor  Observatory,  KS.W. 
Vilsen,  Hanover 
Surrey  •  • 
Wooster,  Ohio,  U.S.A. 

Japan 

Marburg 

Morges,  Switzerland   . . 

Lisbon   . . 

Berlin    . . 

Stonyhurst 

Berlin    . . 

New  Caledonia. . 

San  Salvador,  Central  America 

Transvaal 

Bourbon  Isle    . . 
Munich .  • 


Page 

September,  1883 

163 

99                           91 

154 

99                            99 

154 

99                            99 

155 

October,  1883 

156 

99                      99 

156 

November,  1883 

157 

99                      99 

157 

99                       99 

157 

J'ov.  and  Dec,  1883 

158 

99                              99                  99 

159 

Nov.,  1883,  and 

167 

Jan.,  1884 

December,  1883 

168 

»             »> 

169 

Dec,  1883,  and 

169 

Jan.,  1884 

99                        9« 

169 

December,  1883 

171 

»            » 

172 

»            >i 

172 

January,  1884 

173 

February,  1884 

173 

March  and  April, 

174 

1884 

April,  1884 

177 

April,  1884 

177 

The  Eev.  S.  E.  Bishop/  says  : — 

"  I  would  note  three  peculiarities  of  the  phenomenon,  distinguishing  it  from 
ordinary  sunset  reflections,  and  unlike  anything  I  remember  to  have  observed 
before : — 

"  (1).  It  appears  to  be  a  reflection  from  no  cloud  or  stratum  of  vapour  what- 


ever. 


"  (2).  The  peculiar  lurid  glow,  as  of  a  distant  conflagration,  totally  unlike  our 

common  sunsets. 
"  (3).  The  very  late  hour  to  which  the  light  was  observable — ^long  past  the 

usual  hour  of  total  cessation  of  twilight, 

'*  To  this  may  be  added— 

"  (4).  That  the  centre  of  brilliancy  was  more  or  less  to  the  south  of  west." 

In  a  subsequent  communication,  Mr.  Bishop  tells  us  that  the  after-glow  remained 
brilliant  for  some  time,  and  was  very  bright  on  September  30.  The  haze  stratum  was 
visible,  as  a  continuous  sheet,  at  a  height  far  above  that  of  the  highest  cirrus,  a  slight 


•  *Honololxi  Safcnrday  Press,'  September  22,  1883. 


154  THE  HON.  ROLLO  RUSSELL 

wavy  ripple  being  noticeable  in  its  structure,  always  perfectly  transparent ;  it  was 
invisible  except  under  certain  conditions.  A  conspicuous  circle  of  15°  to  20*^  radius 
was  observed  during  several  days, — "  a  misty,  rippled  surface  of  haze,  with  faint 
crimson  hue,  which  at  the  edges  of  the  circle  gave  a  purplish  tint  against  the  blue 
sky." 

Mr.  L.  Hargrave,  of  Sydney,  N.S.W.,  wrote  as  follows  to  the  'Sydney  Herald' 
on  September  25,  1883: — "With  regard  to  that  pink  glow  that  has  been  so  persistent 
at  sundown  lately,  a  casual  glance  will  convince  most  persons  that  it  is  not  the 
ordinary  red  sunset.  Its  bearing  from  S.W.  to  W.,  and  even  north  of  W.,  is  a  fatal 
objection  to  the  Aurora  Australis  theory,  so  I  hazard  the  opinion  that  volcanic  dust 
is  the  true  solution." 

On  December  29  Mr.  L.  Hargrave  wrote  as  follows  to  the  *  Herald '  (published 
January  2,  1884): — "I  have  observed  the  sun  to  set  in  a  cloudless  sky,  coloured 
orange-yellow;  the  daylight  seems  to  decrease  for  15  or  20  minutes  after  sunset, 
when  I  observe  a  whitish  oval  patch  of  light  at  an  altitude  of  20°  or  30° ;  this  rapidly 
changes  in  colour,  becoming  yellowish-purple,  pink,  brick-red,  and  crimson,  the 
coloured  patch  of  light  at  the  same  time  elongates  and  settles  rapidly  down  on  the 
horizon,  this  phaae  ending  about  45  minutes  after  sunset.  A  second  purplish  patch 
then  appears  at  about  30°  altitude,  the  horizon  turning  to  a  brown  colour.  This 
second  patch  is  more  widely  diffused  and  ita  boundaries  are  more  ill  defined  than  the 
first  one ;  it  changes  to  yellowish-purple,  yellowish-red,  brick-red,  and  crimson, 
spreading  in  azimuth,  and  settles  down  on  the  horizon  in  about  100  minutes  after 
sunset,  when  the  last  tinge  of  colour  disappears. 

The  Rev.  W.  R.  Manley*  wrote  as  follows  from  Ongole,  India : — "  On  September 
10,  11,  and  12,  the  sun  had  a  greenish-blue  tinge,  and  was  somewhat  dimmed  by  a 
haze  in  the  afternoons.  At  4  p.m.  the  colour  was  bluish.  This  gradually  passed  into 
a  greenish  colour,  and  this  in  turn  became  tinged  with  yellow  as  the  sun  approached 
the  horizon.  As  the  sun  sank,  bands  of  smoky  haze  drifted  across  its  disc.  After 
the  sun  was  down,  bright  yellow,  orange,  and  red  appeared  in  the  west,  a  very  deep 
red  remaining  for  more  than  an  hour  after  sunset ;  whereas  under  ordinary  conditions 
all  traces  of  colour  leave  the  sky  in  this  latitude  within  half  an  hour  after  the  sun 
disappears.  At  night  the  moon,  just  past  the  first  quarter,  was  surrounded  by  a  pale 
greenish  halo  about  30°  in  breadth.  Aft;er  sunset  I  observed  a  peculiar  appearance  in 
the  haze  which  covered  the  sky.  It  was  not  of  sufficient  density  to  be  at  all  visible, 
except  where  it  reflected  the  direct  rays  of  the  sun.  There  it  had  a  singular 
mottled  appearance,  with  a  smoky  look  along  the  borders  of  its  denser  portions, 
suggesting  clouds  of  smoke  or  dust  in  the  upper  regions  of  the  atmosphere.  .  .  . 
Ou  the  evening  of  the  13th  the  sun  appeared  to  be  perfectly  clear,  but  after  it  was 
below  the  horizon  the  western  sky  was  seen  to  be  covered  with  a  smoky  haze  of  a 

•  *  Nature,'  vol.  xxviii.  (1883),  p.  576. 


ON  THE  UNUSUAL  TWILIGHT  GLOWS.  155 

singular  appearance,  which  became  brilliantly  illuminated  with  yellow,  orange,  and 
red,  in  the  order  I  have  mentioned,  counting  upward  from  the  horizon.  These  sank 
one  after  another,  leaving  at  last  an  arc  of  brilliant  red  along  the  west ;  the  inner 
portion  of  the  segment  contained  by  the  arc  being  composed  of  orange.  This  disap- 
peared in  turn,  and  the  whole  western  sky  became  yellow  again  without  any  distinct 
outlines  ;  and  this  gradually  deepened  into  red,  which  remained  for  an  hour  or  more 
after  sunset.  The  latter  phenomenon  was  not  unlike  an  ordinary  sunset,  except  in 
brightness  and  duration.     .     .     ." 

The  following  is  an  extract  from  the  account  sent  us  by  Mr.  H.  Parkek, 
of  Hambantota,  Ceylon,  referring  to  the  various  phenomena  seen  in  Ceylon  in 
September,  1883 : — '*  For  several  evenings  previous  to  the  first  green  appearance 
of  the  sun  (September  9)  we  had  magnificent  sunsets,  the  sky  in  particular 
being  of  most  peculiar  and  varying  shades  and  colours,  in  which  delicate,  beautiful, 
blue-and-reddish-purple  predominated,  more  like  the  aurora  borealis,  but  brighter 
and  deeper  in  tone  than  any  I  have  seen  in  the  atmosphere. 

"  September  24. — Just  before  sunset  we  observed  the  same  green  appearance  in 
the  sky  and  over  the  sun  s  disc  as  before,  but  not  so  vivid  a  colour.  The  greenness 
was  very  noticeable  for  some  considerable  distance  around  the  sun,  tinging  even  the 
surrounding  clouds,  which  were  high.  The  sun's  disc  was  clearly-defined,  greenish- 
yellow,  but  around  it  the  green  was  much  more  distinct.  .  .  .  There  was  also  a 
hazy  appearance  in  the  whole  sky,  especially  noticeable  just  after  sunset,  when  the 
general  colour  became  peculiar  and  blue-leaden,  except  in  the  quarter  where  the  sun 
had  set,  where  the  zodiacal  light  was  whiter.  Fully  half  an  hour  later  the  sky 
was  still  of  this  blue-Jeaden  colour,  and  in  the  west  of  a  dull  orange  glow,  rather 
bright  near  the  point  of  sunset.  The  stars  afterwards  were  not  perceptibly 
obscured.  Immediately  after  sunset  there  were  broad  distinct  palish  streaks 
pointing  west,  beyond  the  boundary  of  the  zodiacal  light,  apparently  streaks  in 
the  haze. 

"  On  September  25  and  26  the  sunsets  were  similar,  the  sun  in  setting 
slightly  green,  then  a  dull  yellow  glow  near  the  horizon,  and  a  blue-leaden  sky  long 
after  sunset." 

Dr.  C.  Mbldrum,  F.R.S.,*  says  : — "  The  optical  phenomena  which  have  been 
observed,  generally  presented  the  same  features  throughout,  and  do  so  still.  During 
the  greater  part  of  the  day  the  sun  is  surrounded  by  a  circular  patch  of  whitish 
silvery  light,  on  the  outer  borders  of  which  there  is  a  brownish  fringe,  the  diameter  of 
the  whole  varying  from  12°  to  24°  between  8  a.m.  and  4  p.m.,  according  to  the  sun's 
altitude  and  the  state  of  the  atmosphere.  As  the  sun  approaches  the  horizon  the 
silvery  patch  extends  more  and  more  above  than  below  him,  until  at  length  it  is 
entirely  above  him.     It  then  becomes  greyish  watery  looking ;  and  beyond  it,  towards 

•  *  Proo.  Met.  Soc.  of  MauritiuB,'  October  27, 1883. 


156  THE  HON.  ROLLO  RUSSELL 

N.  and  N.  W.  and  S.  and  S,  W.,  the  sky  has  a  brownish  smoky  appearance  down  to 
the  horizon. 

"  At  about  4  minutes  after  sunset  the  sky  becomes  slightly  purplish  at  30°  to  45° 
above  the  point  of  the  horizon  where  the  sun  has  set.  The  purple  soon  becomes  red  ; 
below  the  red  are  orange  and  yellow ;  and  below  them  there  is  a  bluish  band,  into 
which  the  greyish  watery  patch  has  been  gradually  converted.  Along  the  horizon,  to 
the  extent  of  30°  on  each  side  of  the  point  of  sunset,  there  is  generally  a  low 
brownish-yellow  band,  which  seems  to  be  partly  due  to  smoke  from  the  sugar-mills. 
Between  23  and  26  minutes  after  sunset  the  grass,  trees,  &c.,  assume  a  yellowish-red 
colour.  The  red  band,  which  is  the  most  prominent,  commences  about  19  minutes 
after  sunset  at  an  estimated  altitude  of  40°,  and  lasts  21  minutes,  its  width  and 
altitude  decreasing  until  it  vanishes  on  the  horizon.  At  first  it  extends  as  an  arc 
from  W.  by  N.  to  S.W.  When  its  upper  edge  has  descended  to  10°  above  the 
horizon,  it  becomes  fiery  red,  and  when  nearer  to  the  horizon,  dark  red. 

"  The  blue,  yellow,  and  orange  disappear  in  succession  before  the  red. 

'*  ^  about  10  minutes  before  the  disappe€urance  of  the  red  band,  the  sky  above  it, 
up  to  40°  or  45°,  begins  to  assume  a  greyish-green  colour,  and  aft^r  the  red  has 
disappeared  this  large  new  patch  of  colour,  which  is  now  inclining  to  yellow,  is  the 
only  remarkable  feature. 

"  The  upper  part  of  the  new  patch  becomes  red  about  44  minutes  after  sunset,  at 
about  35°  above  the  horizon.  This  second  red  band  lasts  32  minutes,  or  till  1  hr. 
16  mins.  after  sunset.  At  first  it  forms  an  arc  extending  from  W.N.W.  to  S.S.W. 
Below  ft  there  are  narrow  bands  of  orang3  and  yellow,  and  occasionally  below  them  a 
bluish  band,  all  which  disappear  before  the  red.  The  latter  is  most  intense  when  its 
upper  edge  has  an  altitude  of  about  20"^ ;  it  then  deepens  into  a  dark  red,  and  finally 
dies  out  on  the  horizon. 

"  In  the  morning  the  phases  are  reversed.  The  first  red  band,  which  commences 
on  the  horizon  abo\it  1  hr.  16  uiins.  before  sunrise,  corresponds  to  the  second  red  band 
in  the  evening,  and  the  second  red  band  in  the  morning,  which  commences  on  the 
horizon  about.  39  minutes  before  sunrise,  corresponds  to  the  first  red  band  in  the 
evening," 

Mr.  Todd,  C.M.G.,  reported  aa  follows  from  the  Observatory  at  Adelaide,  South 
Australia,  in  October,*  1883  : — 

"  On  every  clear  evening  dimng  the  month  a  peculiar  phenomenon  has  been 
apparent  in  the  western  sky.  Shortly  after  sunset  a  red  glow  will  make  its  appear- 
ance at  an  altitude  of  about  50°,  being  very  faint  at  first,  but  as  the  brightness  of 
the  sky^near  the  horizon  dies  away  with  the  receding  sun  the  red  glow  will  exp^tnd 
downwards,  becoming  at  the  same  time  more  brilliant,  until  at  last  the  whole  western 
sky  will  be  lit  up  with  a  beautiful  light,  varying  from  a  delicate  pink  to  a  very 

*  *  Stmons'8  Monthly  Meteorological  Magazine,'  vol.  xix.  (1884),  p.  78. 


ON  THE   UNUSUAL  TWILIGHT   GLOWS.  157 

intense  scarlet,  and  presenting  a  very  brUliant  spectacle.  The  upper  part  will  then 
gradually  fade  away  until  the  colour  is  noticeable  only  7^  or  8°  above  the  horizon,  at 
which  time  the  light  is  at  its  brightest.  Afterwards  a  secondary  glow  will  sometimes 
make  its  appearance  at  an  altitude  of  about  50°,  and  again  gradually  spread  down- 
wards until  the  sky  is  again  lit  up.  In  the  secondary  phenomenon  the  sky  is 
generally  more  delicate.  The  whole  thing  will  fade  away  at  about  8  p.m.  This 
phenomenon  has  been  noticed  all  over  the  S.E.  portion  of  this  continent,  from  Port 
Augusta  to  Melboiume."' 

In  a  great  part  of  northern  Grermany,  on  the  evening  of  November  27  and  early 
on  the  28th,  a  peculiar  light  phenomenon  was  seen,  of  which  a  correspondent  at 
Magdeburg  wrote*  : — "  Already,  at  5.30  a.m.,  a  reddish  glow  of  the  twilight  arc  was 
seen  in  the  S.S.E.,  which  quickly  augmented  in  breadth  and  height ;  the  splendour 
of  coloimg  was  not  quite  equal  to  that  of  the  preceding  evening,  but  towards  6.30  the 
whole  sky,  from  N.E.  to  S.,  seemed  to  be  bathed  in  shining  pm-ple.  At  6.45  the 
carmine  tint  predominated,  which  appeared  in  a  very  distinctly  marked  flat  arc.  At 
7  a.m.  the  more  elevated  arc  was  of  so  pale  a  yellow  brightness  that  one  might  sup- 
pose that  the  sun  had  already  risen.  .  .  .  The  sun  rose  at  7.43.  On  the  evening 
of  November  27  the  time  of  the  visibility  of  the  arc  was  2  hrs.  13  mins. ;  on  the 
morning  of  the  28th  also  2  hrs.  13  mins." 

Herr  Dr.  A.  Gekb£R  wrote*  from  GlQckstadt  as  follows  : — 

"  The  phenomenon  was  most  fiilly  developed  here,  as  elsewhere,  from  November  26 
to  December  1,  but  did  not  suddenly  cease  at  the  latter  date,  for  there  was  an 
unusual  colour  in  the  sky  for  many  days,  more  particularly  before  sunrise.  The 
display  of  November  29  was  the  grandest  and  most  manifold,  and  I  give  a  description 
as  exactly  as  possible  of  this  one,  as  its  overwhelming  magnificence  still  presents 
itself  to  me  as  if  it  had  been  yesterday.  When  the  sun  had  set  about  a  quarter  of 
an  hour  there  was  remarkably  little  red  (or  ordinary)  after-glow,  yet  I  had  observed 
a  remarkably  yellow  bow  in  the  south,  about  10°  above  the  horizon.  Soon — ^that  is, 
after  about  10  minutes  more,  when  it  was  at  least  half-past  fom- — ^this  arc  rose  pretty 
quickly,  extended  itself  aU  over  the  east  and  up  to  and  beyond  the  zenith.  The 
sailors  declared,  *  Sir,  that  is  the  Northern  Lights  1 '  and  I  thought  I  had  never  seen 
Northern  Lights  in  greater  splendour.  After  5  minutes  more  the  light  had  faded, 
though  not  vanished,  in  the  east  and  south,  and  the  finest  pm-ple-red  rose  up  in  the 
S.W.  ;  one  could  imagine  oneself  in  Fairyland.  The  S.W.  sky  was  bathed  in  an 
immense  sea  of  light  red  and  orange,  and  till  more  than  1^  hours  after  sunset  the 
colouring  of  the  sky  was  much  more  intense  than  it  is  half»an-hour  after  a  very  fine 
sunset  in  ordinary  conditions." 

Mr.   John  Tebbutt,   F.R.A.S.,   of    Windsor   Observatory,    N.S.W.,    wrote  as 
foUowst  on  November  15,  1883  : — 

•  *  Met.  Zeitschrift,'  vol.  i.,  p.  185. 
t  *  Sydney  Herald.* 


158  THE   HON.  ROLLO  RUSSELL 

**The  appearance  presented  by  our  evening  skies  for  some  weeks  past  has  been 
the  subject  of  general  remark. 

"Last  evening,  November  14,  the  sky  was  almost  cloudless  after  sunset,  and  the 
usual  brick-red  light  again  made  its  appearance  along  the  west-south-west  horizon. 
It  was  reflected  apparently  from  an  almost  invisible  and  gauze-like  cloud  in  the 
higher  regions  of  the  atmosphere.  About  7  o'clock  the  red  glow  was  at  its  maximum, 
when  a  solitary  cloud,  whose  apparent  siuface  did  not  exceed  ten  square  d^rees, 
presented  itself  above  it  at  an  altitude  of  25°,  This  cloud,  which  was  at  first  white, 
quickly  changed  to  a  beautiful  green,  its  borders  being  of  a  deeper  tint  Of  all  the 
cloud  phenomena  that  I  have  witnessed,  it  was  one  of  the  most  remarkable.  It 
retained  its  green  colour  for  the  space  of  about  10  minutes,  being  aU  the  time  subject 
to  much  internal  commotion.  It  soon  afterwards  resolved  itself  into  several  cloudlets 
and  finally  disappeared.  Two  or  three  other  small  clouds  were  visible  at  the  same 
time,  and  about  the  same  altitude  above  the  northern  horizon ;  but  these  were  of  a 
grey  colour  throughout.  The  eastern  sky  about  the  moon  was  of  that  deep  blue 
which  is  frequently  observed  to  surround  her  when  rising  during  the  winter  opposi- 
tions. Shortly  after  the  dispersion  of  the  green  cloud  the  ruddy  glow  gave  place  to 
the  ordinary  pale  gray  of  the  twilight,  but  by  half-paat  seven  o'clock  the  western 
sky  became  diffused  with  red,  but  this  time  of  a  clearer  and  more  aurora-like  tint. 
It  did  not  appear,  as  in  the  former  case,  to  be  reflected  from  hazy  cloud,  and  it 
extended  much  higher  in  the  sky,  This  repetition  of  the  ruddy  glow  on  the  same 
evening  is  a  phenomenon  which  I  had  witnessed  on  several  occasions  during  the 
present  month.  I  remember  that  many  years  ago  (probably  twenty-five)  a  somewhat 
similar  patch  of  red  light  used  to  make  its  appearance  regularly  after  sunset  in  the 
west-north-west.  This  phenomenon  occurred  previously  to  the  commencement  of  my 
regular  meteorological  observations  in  1863,  and  was,  I  think,  contemporaneous  with 
a  very  dry  winter. 

**  That  the  present  ruddy  akies  are  not  merely  a  local  phenomenon  is  obvious 
from  the  fact  that  during  the  past  three  months  they  have  been  regularly  observed 
over  a  considerable  portion  of  the  Indian  Ocean." 

Herr  G.  Meyer  wrote,*  at  the  end  of  December,  as  follows  : — 

"  The  twilight  phenomena  occurred  here  from  the  26th  of  November,  and  lasted 
till  5.45  p.m.  On  the  last  days  of  November  their  course  was  such  that  at  first  a 
strong  evening  redness  developed  itself,  which  lasted  till  4.30  (and  similarly  a  moruing 
redness).  At  this  time  the  whole  sky  shone  with  a  yellowish  colour,  and  from  4.45  a 
purplish  glow  developed  itself,  which  attained  its  maximum  at  5,  and  sank  down  to 
the  horizon  till  5.30.  On  other  days  these  periods  were  not  so  sharply  distinguish- 
able. On  December  19  the  phenomenon  was  absent.  On  December  5  the  moon  had 
a  large  circular  corona.     The  sky  is,  in  a  striking  degree,  never  pure,  even  with  a 

•  *Met.  Zeitschrift,'  vol.  i.,  p.  161. 


ON  THE   UNUSUAL  TWILIGHT  GLOWS.  159 

high  barometer  and  calm  weather  ;   in  weather  otherwise  clear  the  sun  is  surrounded 
with  a  sheen." 

The  following  are  local  notes  taken  in  Surrey  by  the  Hon.  F.  A.  Rollo  Russell 
(MS.  Register)  :— 

*'  The  first  sunset  which  showed  any  effects  of  a  very  striking  or  extraordinary 
character  was  on  November  9,  1883 ;  but,  on  referring  to  private  notes  taken  daily 
during  the  summer  and  autumn,  I  find  that  as  early  as  September  8  a  '  fine  red 
sunset  with  after-glow'  is  mentioned,  and  this  is  worth  remarking,  because  I  had 
never  previously  used  the  expression  *  after-glow.' 

"  On  September  9  a  *  great  succession  of  small  cirrus-like  masses '  was  noted, 
'  and  fibres,  clearly  marked ;  very  high  small  cirro-cumulus,  vastly  higher  than  the 
cirrus,  also  high.  Beautiful  rainbow  colours  in  cirrus  and  cirro-cumulus  near  the  sun. 
All  coming  from  W.  against  surface  wind.'  The  remarkable  feature  in  this  condition 
was  the  great  elevation  of  the  cirro-cumulus  above  the  cirrus,  and  the  colours  were 
certainly  quite  imcommon. 

"  On  September  26  there  were  '  light  pink  cirrus  stripes  '  at  sunset. 

*'  On  October  3  there  was  a  *  red  and  yellow  sunset.' 

"  On  October  20  there  was  a  *  fine  reddish  sunset,  with  bright  isolated  cloud 
and  slight  low  cirrus.' 

"  On  October  21a'  fine  reddish  and  orange  sunset.' 

"  On  October  22  '  simset  in  bath  of  cirrus ;  halo  effect,  red.  Rest  of  sky 
clear.' 

"  On  October  23  a  '  clear  sky,  but  white  mistiness  on  horizon '  at  sunset. 

*'  On  October  27  '  fine-weather  sunset ;  some  streaks  of  soft  delicate  cirrus  in 
irregular  patches,  turning  fine  pink  at  sunset ;  glow  from  horizon.' 

"  On  November  8  a  '  fine  sunset,  with  straight  horizontal  lines  of  cirrus  (?)  and 
very  slight  bank.  Long  after  sunset,  and  till  nearly  dark,  a  pink  glow  fi:om  some 
very  high  filmy  cirrus." 

The  foDowing  is  transcribed  fi^om  the  notes  taken  on  November  9  : — "  Series  of 
ripple  cirrus  in  web-Uke  uncrossed  strise,  transverse ;  well-defined  morsels  of  high 
cixro-cumulus  ;  some  cirro-stratus.  At  7.30  a.m.  there  was  some  high  pink  filmy 
cirrus,  Uke  last  night.  11.20  a.m. — Blue  sky,  but  some  large  patches  of  very  high 
cirro-cumulus,  one  overhead  ;  smallest  fleeces ;  part  consisting  of  re-curved  waves  or 
bars,  smalL  .  .  .  Heavy  shower  1.50  to  2.5  p.m.  Fine  after  this  shower ;  sky 
cleared  of  cirrus  and  cirro-cumulus,  and  general  appearance  quiet.  .  .  Sun  set  in 
very  slight  haze  bank  or  cirrus ;  remarkable  whitey-greenish  opalescence  above  sun 
at  sunset.  About  15  minutes  after  sunset  the  sky  in  W.S.W.,  from  near  the  horizon 
up  to  about  45°,  was  of  a  briUiant  but  delicate  pink.  Below  this  a  very  curious 
opalescent  shining  green  and  sUghtly  greenish-white,  the  pink  opalescence  going 
off  into  bronze-yellow,  and  that  to  the  green  tint.      The  coloured  portion  of  the 

y2 


160  THE   HON.  ROLLO  RUSSELL 

sky  spread  out  like  a  sheaf  from  the  horizon,  and  apparently  consisted  of  a  very 
high  thin  filmy  cirrus  disposed  in  transverse  bands,  or  ripples,  close  together,  and 
very  delicate  in  form,  outline,  and  tint.  At  sunset  some  morsels  of  cirro-cumulus 
were  lighted  up  with  a  light  red  fading  to  a  deep  red,  but  this  soon  passed  off. 
What  remained  seemed  not  to  belong  to  clouds,  but  to  glow  of  itself,  like  some 
super-atmospheric  film.  The  bright  pink  colour  continued,  and  even  increased  in 
brightness,  and  at  5  o'clock  cast  a  fine  glow  over  the  east  hills  and  on  objects 
exposed  to  it.  The  moon  was  shining  brightly.  The  colour  now  began  slowly  to 
recede  towards  the  horizon  from  the  part  most  nearly  overhead,  and  left  a  clearly 
visible  filmy  ripple  of  cirrus  (apparently)  of  a  soft  grey.  When,  however,  at  5.25, 
the  greater  part  of  the  colour  was  gone,  and  it  remained  bright  only  near  the  horizon, 
it  began  to  grow  again,  and  in  a  short  time  (5.32)  the  whole  extent  of  the  film  was 
again  glowing  bright  pink,  producing  a  very  striking  effect  in  contrast  with  the 
silvery  moon,  dark  sky,  and  bright  stars  in  the  north  and  east.  It  was  now  almost 
dark,  except  for  the  moonlight  and  the  cirrus  glow.  The  pink  light  then  slowly 
withdrew  towards  the  horizon,  remaining  bright  and  deep-coloured  there  till  5.50. 
At  5.58  the  last  pink  colour  disappeared.'  The  sight  was,  altogether,  a  very  extra- 
ordinary one,  and  unlike  any  in  the  writer's  experience.  It  was  remarkable,  first,  for 
the  light  filmy  character  of  the  cloud  (if  cloud  it  was)  ;  next,  for  the  wavy  form  of 

Fig.  13. — Diagram  of  Sunset  Colours 


Blue  -^  ^  -~^^^^\/:_L^^~    '-^  Slue 

Sky  ^^'^^^A^'^'^^-^ll         .^^mZ^^  Ski/ 

V        WAtU     ■  -w^ 

Bright  opalescent  Jillout 

^^^^^  andWute  Grten 

Gtttn  Bright  Green  Green 

Opalescent 
Green  ha^e  Pink 

HORIZON__— HORIZON 

SUN  C\ 

the  clo\id ;  thirdly,  for  the  bright  green  glow  near  the  place  where  the  sun  set,  and 
the  strange  yellow  light  above  the  green ;  fourthly,  for  the  very  long  endurance  of 


ON   THE   UNUSUAL  TWILIGHT   GLOWS.  161 

the  whole  phenomenon.  It  was  supposed  to  be  due  to  cirrus  or  a  high  kind  of  cloud, 
because  (l)  similar  clouds  stretched  in  long  streaks  southwards  and  over  the  S.E. 
horizon,  and  the  glow  remained  long  in  these  streaks ;  (2)  when  the  light  retired  it 
remained  visible  as  silvery-grey  cloud  ripples  before  the  second  after-glow  re-kindled 
it ;  (3)  because  the  colour  became  (but  very  graduaUy)  darker  as  time  went  on,  and 
the  recessions  towards  the  west  followed  the  sun.  There  was  no  apparent  movement 
of  the  cloud  during  the  time  of  the  display ;  the  form  remained  the  same  throughout, 
and  was  distinguished  by  the  clear  demarcation  of  the  film  towards  W.  and  E.,  the 
cessation  of  the  cloud  and  the  glow  towards  the  zenith,  and  the  long  streaks  stretch- 
ing apparently  horizontally  near  the  horizon.  The  sunset  light  of  the  sun  was 
peculiarly  yellow.  The  ripples  of  the  luminous  film  were  transverse  to  the 
sun's  rays. 

"  On  November  10,  at  6.20  a.m.,  there  was  '  a  pink  sunrise  light  in  the  extreme 
east,' the  rest  of  the  sky  being  cloudy.  During  the  afternoon,  about  3.30  p.m.,  and 
later,  *  a  very  thin  high  cirrus  ripple  haze  became  visible  in  parts  of  the  sky,  especially 
S.W.  About  4.32  this  became  more  distinct  as  it  began  to  glow  with  the  light  of 
the  clear  sunset  (4.18),  and  became  bright  pink,  lasting  till  5.10.  As  the  light  faded 
off  it,  it  entirely  disappeared  in  the  deep  blue  sky.  The  ripple  was  very  small,  close, 
and  fine,  and  lay  to  the  left,  or  south  of  the  place  of  sunset,  up  to  about  25°  from 
the  horizon.* 

"  On  November  11  there  was  pink  cirrus  in  the  E.  at  6.10  a.m. 

*'  On  November  17  the  simset  was  clear. 

"  On  November  19  there  was  a  '  clear  sunset  with  white  mist.' 

"  On  November  23  there  was  *  sunset  in  cirro-stratus  or  cirrus  bath.' 

"  On  November  24,  ^  after  sunset  yellowish-green  striae  in  W.' 

"  On  November  25,  *  sunset  in  amorphous  indistinguishable  cirro-stratus  or  cirrus 
haze.  Green  light  above  sunset,  and  bright  greenish-white  growing  from  about 
10  minutes  after  sunset.  Above  the  greenish -white  pale  red  or  pink.  Lasted  about 
45  minutes  after  sunset.  The  sky  shone  somewhat  as  on  November  9,  but  much  more 
feebly.' 

"  On  November  26  similar  phenomena  occurred  more  strongly,  and  lasted  nearly 
an  hour.     Also  on  November  27,  lasting  till  5.20. 

"On  November  28  the  glow  began  about  25  minutes  after  sunset,  and  was 
succeeded  by  a  faint  brass-coloured  secondary  glow. 

"  On  November  29  a  similar  glow  was  seen  through  breaks  in  the  clouds,  and 
the  newspapers  gave  an  account  of  an  extraordinary  redness  in  the  sky  from  5.30  to 
7.30  a.m. 

"  On  November  30,  at  6.5  a.m.,  there  was  a  fine  deep  red  glow  in  the  E.  This 
spread  quickly  upwards,  and  had  turned  yeUow  by  6.40.  At  6.24  the  faint  redness 
extended  to  the  zenith.  There  was  no  cirrus  visible,  but  some  cirro-cumulus  remained, 
tipped  with  duU  red  from  6.5  to  7.44,  when  the  sun  rose. 


162  THE   HON.   ROLLO   RUSSELL 

"  On  December  4,  when  the  sky  was  again  clear,  the  first  redness  appeared  in 
the  E.  at  6.5,  and  at  6.10 'was  quite  bright,  like  the  reflection  of  a  fire.'  It 
appeared  continuous  and  without  defined  shape.  By  6.30  the  red  had  slowly  changed 
to  a  saffron  colour,  and  being  seen  less  in  perspective,  seeraed  less  concentrated.  The 
reflecting  matter,  or  a  part  of  it,  was  now  seen  to  consist  of  ill-detined  streaks  and 
patches  of  misty  cloud  of  some  sort,  in  which,  after  long  watching,  no  motion  oould 
be  detected.  At  6.45  some  of  these  streaks  were  illuminated  nearly  overhead  south- 
wards of  a  pale  straw  colour  and  bluish-white,  and  their  outlines  were  distinct.  Most 
of  the  streaks  stretched  about  W.S.W.  to  E.N.E.,  and  towards  the  N.E,  the 
appearance  was  like  a  fretwork  of  the  lightest  wavy  mist.  From  6.30  to  6.50  the 
glow  was  of  a  sickly  yellowish-green,  with  a  pale  pink  towards  the  zenith,  and  a 
rather  ghastly  white  glare  below.  At  6.53  a  second  glow,  much  brighter  than  the 
first,  appeared  in  the  E.S.E.,  of  a  deep  red  colour,  quickly  turning  to  orange.  This 
glow  was  in  a  bank  or  arc  much  better  defined  along  the  top  than  the  first.  At 
7.10  it  had  turned  quite  yellow,  and  had  grown  up  to  about  15°.  At  7.16  the 
last  star  disappeared  m  the  bright  light  which  was  now  cast  on  all  objects  towards  the 
W. ;  the  clear  sky,  as  the  light  touched  the  thin  high  mist,  appearing  progressively 
veiled.  Just  before  the  advent  of  the  second  glow  the  thin  cloud  streaks  had  nearly 
vanished,  but  as  this  new  light  grew  and  changed  to  bright  yellow  they  became  again 
illuminated.  At  7.12  the  upper  part  of  arc  No.  2  was  yellow,  with  a  greenish-white 
central  part  below.  At  7.20  the  part  below  the  arc,  and  along  the  horizon  south  and 
north  for  some  distance,  was  a  peculiar  steely  bluish-yellow,  and  the  upper  (at  an 
altitude  of  about  50°)  pink.  These  effects  slowly  diminished,  but  the  steel  colour 
remained  tiU  sunrise.  At  7.23  the  sky  overhead  and  towards  the  W.  was  faint  pink, 
with  large  billowy  streaks  and  patches  like  murky  cirrus,  without  fibrous  structure. 
This  cloudy  appearance  was  sufficient  to  hide  the  blue  sky,  when  the  cloudy  matter 
wafi  illuminated  from  below ;  but  in  fuD  daylight  only  faint  traces  remained.  At 
7.50,  and  for  some  time  after,  this  cloudiness  was  again  made  plainly  visible  by  the 
rising  sun,  as  by  the  first  and  second  glow.  Twelve  minutes'  careful  watching  failed  to 
discover  in  them  any  uniform  progressive  motion,  though  their  shape  slightly  changed. 
The  sun  rose  at  7.55,  of  a  red  colour,  but  in  about  half  an  hour  was  pale  steely-bluish 
white,  and  surrounded  by  a  silver- white  sky,  with  a  slight  bluish  tinge.  During  the 
day  the  billowy  high  mist  was  faintly  visible,  but  the  sky  was  bright  blue.  As  the 
sun  was  setting  (3.53)  this  high  haze  became  so  white  by  reflection  that  the  sky 
looked  quite  clouded  with  it.  Nothing  otherwise  remarkable  appeared  till  4.12,  when 
it  was  evident  the  phenomenon  would  recur  ;  the  central  spot  above  the  sun's  place 
being  bright  steel  or  lead  colour,  and  the  parts  round  it  a  metallic  pink,  this  has 
been  the  usual  preliminary.  The  sky  in  the  east  was  rosy.  The  rose  colour  quickly 
passed  over  towards  the  west,  and  about  4.20  the  whole  sky  between  the  western 
horizon  and  the  zenith  was  flushed  with  red.  At  this  stage  the  forms  of  the  haze- 
billows  and  streaks  seemed  to  be  lost  in  the  uniform  rosy  glow  ;  this  glow  slowly  sank 


ON  THE  UNUSUAL  TWILIGHT    GLOWS.  163 

down  to  the  horizon  as  usual.  At  4.25,  or  thereabouts,  the  crescent  moon  appeared 
blue  in  this  pink  haze,  but  in  a  few  minutes  was  left  behind  and  appeared  much  as 
usual.  The  small  stormy  scud  from  N.  was  lighted  up  pink  against  a  deep  blue  and 
green  sky  towards  the  E.  and  overhead,  and  in  the  S,W.,  near  the  moon.  As  the 
glow  sank  westwards  the  sky  seemed  perfectly  clear,  without  a  trace  of  the  billowy 
haze.  At  4.35  the  bank  of  light  was  very  bright.  About  4.45  it  was  lost  to  view 
behind  low  clouds;  as  it  approa)3hed  the  horizon  the  sky  again  became  mottled  with  the 
reflecting  haze,  which  assumed  a  straw-coloured  tint.  This  pale  light  again  sank 
westward  and  vanished  soon  after  5  ;  the  moon  and  stars  gave  no  indication  of  a  haze 
canopy.  It  seemed  to  be  without  motion,  and  was  disposed  in  ver}^  large  billows, 
their  length  lying  about  S.W.  to  N.E.  on  both  sides  of  the  glow,  but  crossed  in  some 
parts  by  a  thick  streak  nearly  at  right  angles. 

"On  December  5,  *  exactly  at  6.5  a.m.  the  first  faint  red  blush  grew  up 
quickly  from  the  E,S,E.,  and  in  7  or  8  minutes  had  increased  largely  in  brightness 
and  extent.  The  night  was  very  fine  and  clear  and  the  soft  crimson  .glow  banging 
above  the  horizon  in  the  darkness  produced  an  interesting  efiect.  It  grew  rapidly  up 
towards  the  zenith,  and  at  6.18  formed  an  arc,  of  which  the  highest  point  was  about 
40**  from  the  horizon.  After  this  it  quickly  changed  to  orange  and  yellow,  and  the 
colours  went  off.  The  arc  was  more  southerly  than  yesterday,  and  the  peculiar  light 
reached  from  S.S.W.  to  N.N.E.  At  6.55  the  second  glow  began  ;  and  rising  up  quickly, 
produced  a  fine  red  arc,  less  bright  than  that  of  yesterday  morning.  At  7.6  the  arc 
was  olive-green  below,  yellow  in  the  central,  and  pink  in  the  outer  parts,  and  hardly 
any  cloud  structure  could  be  discerned.  What  there  was,  however,  seemed  to 
resemble  the  film  of  yesterday.  The  upper  edge  of  the  glow,  as  it  advanced,  was 
pretty  well  marked,  and  at  7.12  it  crossed  the  zenith  and  passed  north-westwards, 
covering  a  bright  star  in  that  direction  with  a  thin  pink  veil,  This  star  continued 
visible  till  7.21.  The  sky  after  this  time  was  pale  yellow,  and  little  of  an  uncommon 
character  remained,  except  the  greenish  light  in  the  east,  Sunrise,  7.51,  red  sun, 
turning  sUvery-white  later,  Sunset,  3.50,  in  hazy  striae.  At  4.15  yellow  glow 
appearance  began  and  went  through  usual  changes,  The  light  was  pink  overhead 
about  4.25,  and  the  margin  (ulterior)  passed  over  about  4,26.  The  glow  grew  more 
and  more  red,  as  usual,  in  sinking  down,  exhibited  spokes  of  rays,  and  disappeared  at 
4.45.  The  second  illumination  was  brightest  about  5.5  and  disappeared  a  few  minutes 
later.  At  430  the  moon  looked  blue,  like  yesterday,  in  a  pink  haze.  The  horizon 
was  misty.     The  crescent  moon  shone  all  the  evening  with  a  greenish  light. 

"  On  December  7  it  was  remarked  that  the  reflecting  matter  in  the  west  after 
sunset  first  shone  with  the  rays  of  the  setting  sun  between  20  and  29  minutes  later 
than  the  cirrus  above  which  it  floated. 

"  On  December  ]  1  the  sky  was  perfectly  clear  and  cloudless  about  an  hour  before 
sunrise,  except  a  little  detached  scud.  At  7.21  a.m.,  as  the  light  of  the  primary 
glow  spread  to  the  zenith,  the  sky  was  seen  to  be  striped  with  very  high  filmy  streaks 


164  THE  HON.   ROLLO  RUSSELL 

in  the  S.E.  At  7.32  this  appearance  extended  over  the  N.W.  Obtaining  a  good 
view  of  the  streaks  in  the  S.E.,  I  tried  to  discover  their  motion.  After  about  10 
minutes'  watching,  one  of  them  showed  a  translation  from  W.N.W.  of  about  half  an 
apparent  solar  diameter  in  that  time.  At  7.35  and  7.40,  the  whole  sky  being  covered 
with  these  long  thin  stripes,  like  the  "  billows  "  of  a  few  days  before,  but  not  so  wide, 
it  was  found  that  they  extended  on  aU  sides  from  south  to  north  or  S.  by  W.  to  K. 
by  E.  One  point  seemed  worth  special  notice.  Those'  in  the  extreme  west,  that  is, 
10°  or  so  above  the  horizon,  as  weU  as  in  the  east,  did  not  appear,  like  ordinary  cirrus 
lines,  to  radiate  from  a  point  on  tbe  horizon.  On  the  contrary,  they  were  all  seen 
CO  be  lying  in  the  same  direction,  and  the  stripe  furthest  to  the  west  gave  nearly 
as  good  an  idea  of  its  true  direction  as  a  stripe  overhead.  The  eye  made  the 
necessary  allowance  for  such  appearance  of  convergence  as  there  was  ;  and  they  were 
at  once  seen  to  be  parallel.  At  1  p.m.  the  streaks  of  sky-haze  reappeared,  stretching 
from  S.S.W.  to  N.N.E.,  and  were  watched  without  any  motion  showing  itself,  though 
when  looked  at  after  the  lapse  of  15  or  20  minutes  they  seemed  to  have  moved  a  little 
transversely  eastwards.  Their  very  indefinite  appearance  in  the  daytime  made  exact 
observation  difficult,  and  at  times  the  strong  sunshine  seemed  to  obliterate  them 
altogether.  .  .  .  At  2  p.m.  a  stripe  of  upper  haze  in  the  S.S,E.  was  watched 
for  10  minutes,  and  no  motion  discovered,  either  transverse  or  longitudinal.  The 
stripes  were  observed  through  dark  glasses,  which  increased  their  visibility.  At  4. 1 5 
green  spot  about  10**  above  horizon.  Pink  up  to  and  beyond  zenith,  and  on  both 
sides.  Small  cirri  from  sunset  till  4.10  pink,  then  light  dusky  green.  Whole  sky  at 
4.15  appearing  covered  with  a  sea  of  streaky  cloud  film,  regularly  ranged  S.S.W.  to 
N.N.E. ;  no  appearance  of  a  radiant  point.  At  4.20  spot  of  green  being  closed  in  by 
bright  pink  all  over  western  sky  ;  4.23,  pink  seemed  to  pass  zenith.  .  .  .  At 
4.30  pink  edge  about  22°  from  horizon.  Green  sunk  beyond  horizon.  At  4.36  pink, 
about  15^  Sky  blue.  At  4.41  edge  of  red  glow  about  10°  above  horizon.  Sky 
beginning  to  be  lighted  up  from  below,  and  to  appear  cloudy  again.  At  4,48,  blood- 
red  to  about  7°,  Cirri  in  E.  peculiar  dull  pink.  Moon  very  slightly  bluish.  4.55 
last  red  disappeared.  Second  glow  just  past  zenith.  Usual  phenomena  of  second 
glow,  like  first  over  again,  but  less  bright.  At  5.18  red  arc  very  fine.  Almost  gone 
5.30.     Just  visible  5.33. 

"  On  December  15  there  was  ^  a  yellow  glow  in  the  S.E.  at  6.18  a.m.,  which  grew  up 
as  usual.  Very  fine  clear  sky  with  bright  greenish  moon  (full)  in  the  W.  Not  the 
slightest  halo  or  corona  by  the  moon  during  night  or  morning.  Greenish  light  above 
sun  at  sunrise,  kc.  Sky  now  (7.40)  seems  to  be  streaked  with  haze  billows  (length 
S.S*W.  to  N.N.E.)  as  on  previous  days.  The  western  sky  showed  this  marking  very 
clearly  at  this  time,  but  it  quickly  became  less  and  less  visible  towards  sunrise.  It 
remained  visible,  however,  over  the  S.E.  for  a  long  time,  and  after  sunrise  for  at  least 
three  quarters  of  an  hour.  The  western  sky,  at  7.40,  looked  as  if  covered  with  a 
cloud  of  a  streaky  cirrus  character,  only  more  regulai'ly  disposed  in  bands,  like  a  great 


ON  THE   UNUSUAL  TWILIGHT  GLOWS.  165 

ocean  covered  with  regular  billows.  There  were,  however,  some  spaces  clear.  At  8 
all  this  (in  the  west)  had  melted  into  blue  again.  From  8  to  8.30  a.m.  I  watched  the 
distinct  streaks  in  the  S.S.E.,  the  branches  of  an  oak  giving  the  means  of  discovering 
motion  in  any  direction.  Half  an  hour's  watchiug  failed  altogether  in  detecting  the 
slightest  general  movement,  though  there  was  a  slight  change  in  the  breadth  of  one 
of  the  streaks.  After  the  sun  had  risen  about  a  quarter  of  an  hour,  the  stripes  in 
the  W.N.W.  again  grew  quite  distinct,  but  did  not  .obliterate  the  blue  sky  as 
before." 

In  fiirther  daily  notes  on  the  sky-phenomena,  the  following  points  may  be 
mentioned : — 

'*  On  December  21,  the  clouds  remained  red  1  hr.  15  mins.  after  sunset.  At  4.22 
p.m.  the  cloudy  matter  or  high  haze  very  unexpectedly  appeared  in  the  west  and 
nearly  overhead,  the  sky  not  having  seemed  transparent  enough  to  show  it.  It  was 
in  the  form  of  a  hazy,  white  ripple,  the  waves  close  together  and  regularly  disposed, 
but  not  all  in  the  same  direction  in  different  parts  of  the  sky.  Some  were  stretched 
from  S.W.  to  N.E.,  others  from  W.  to  E.  and  S.S.W.  to  N.N.E. 

**  On  December  23,  the  evening  glow  was  exceedingly  beautiful,  exhibiting  radiant 
spokes.  About  4.30  the  clear  sky  between  the  zenith  and  the  horizon  became  as  if 
veiled  with  a  very  delicate,  thin,  structiu*ele8S  mist,  which  completely  hid  the  blue. 
This  was  at  first  greenish-yellow  below,  and  then  turned  to  a  very  fine  amber  below 
and  pink  above.  At  about  4.35  the  glow  may  have  been  at  its  highest  point,  about 
35*^  or  40°  above  the  horizon.  It  sank  below  the  horizon  at  about  4.52.  At  about 
5.5  the  secondary  glow  extended  to  the  zenith,  and  remained  an  exquisite  faint  pink 
(near  the  horizon)  till  5.25.  On  both  sides  the  sky  near  the  horizon  was  clear  blue 
or  green. 

"  On  the  last  days  of  December,  which  were  foggy  and  cloudy,  a  pinkish  light 
affected  the  mist  as  early  as  7.30  a.m.,  and  sometimes  after  sunset. 

'*  The  glow  continued  during  January.  On  January  24,  the  hazy  stripes  were 
very  plain  over  the  western  sky,  and  during  the  whole  morning,  in  the  neighbourhood 
of  the  sun,  making  a  sort  of  sheen  close  to  the  sun  ;  their  motion  was  imperceptible 
in  ten  minutes'  watching.  After  sunset  the  ulterior  margin  of  the  glow  passed 
overhead  about  4.57  ;  set  at  5.20.     Second  glow  about  25°  high  at  5.40. 

'*  There  was  a  marked  diminution  of  all  the  effects  at  the  end  of  January,  The 
sun  was  sxnrounded  during  the  day  by  a  brownish-pink,  faint,  and  ill-defined  circle, 
and  between  this  and  the  sun  there  was  a  bluish-white  sheen  or  glare. 

"  In  February,  the  duration  and  intensity  of  the  glow  decreased  further,  and  it 
was  of  a  yellow  colom*,  or  faint  green  and  pink. 

*'  On  March  6,  there  was  a  slight  repetition  of  the  sky-illiunination,  lasting  only 
30  minutes,  but  during  March  the  glare  completely  vanished,  and  no  illumination 
whatever  appeared  in  a  clear  sky  after  sunset.  During  the  remainder  of  the  year 
the  siuisets  were  uncommonly  free  from  colour,  even  promising  skies  turning  grey 


166  THE  HON.  ROLLO  RUSSELL 

Boon  after  sunset,  and  no  redness  of  an  ordinary  character  remaining  along  the 
horizon  after  sunset,  except  on  a  few  evenings  and  in  a  few  localities." 

Local  Notes  taken  at  San  Remo,  Italy,  and  Cannes,  France,  from  January  5  to 
January  14,  1884,  by  the  same  observer  : — 

''  On  January  5  and  6,  the  glow  was  visible  but  not  striking  at  San  Remo.  The 
hazy  streaks  lay  from  S.  W.  to  N.E. 

"  On  January  7,  there  was  a  fine  yellow  after-glow,  lasting  about  an  hour. 

**  On  January  8,  there  was  a  fine  cleax  sunset  with  the  sky-haze  very  distinct  in 
billows  or  streaks  exactly  as  in  England,  but  very  faint,  S.W.  to  N.K  Duration 
about  an  hour,  chiefly  yellow. 

"  On  January  9,  the  sunrise  was  extremely  clear  and  fine.  The  time  from  strong 
•twilight  to  sunrise  was  61  minutes,  from  the  primary  glow  at  about  5*^  to  sunrise 
41  minutes.  Before  sunset  the  streaks  again  appeared  in  an  intensely  dear  blue 
sky,  about  S.W.  by  W.  to  N.E.  by  K  About  10  minutes  after  sunset  the  sky  was 
beautifully  rosy  in  the  east  and  slightly  rosy  in  the  north,  and  towards  the  zenith 
in  the  west.  In  the  west  bright  peacock  green.  At  23  minutes  past  sunset  the  upper 
margin  of  the  pink  passed  the  zenith.  The  west  now  turned  bright  yellow.  At 
35  minutes  past  sunset  the  red  was  lost  in  the  yellow  western  sky.  At  37  minutes 
the  edge  was  about  10^  above  the  horizon.  A  beautifiU  secondary  glow  appeared  at 
55  minutes,  the  evening  star  looking  blue  through  the  pink  haze. 

*'  On  January  10,  the  air,  sky,  and  horizon  were  perfectly  clear.  At  22  minutes 
before  sunrise  a  beautiful  piu*plish^pink  film  extended  between  about  40°  above  the 
eastern  horizon  and  the  zenith.  Below  this  in  the  east  was  a  green  sky,  and  along 
the  horizon  an  orange  band,  which  no  doubt  was  the  ordinary  effulgence  of  simrise. 
All  the  sky  colour  soon  went  except  the  strange  green  i^  the  east.  The  sun  rose  like 
a  gush  of  white-hot  iron,  instantaneously  brilliant,  fron^  the  sea  line.  Corsica,  over 
100  miles  distant,  was  very  clearly  defined.  The  streaks  in  the  sky  appeared  as 
usual  before  sunrise,  and  were  lying  StW.  by  W»  to  N.E.  by  K,  obliquely  to  the  rays 
of  the  rising  sun. 

"  At  sunset  all  the  atmospheric  conditions  were  absolutely  perfect  for  separating 
the  sky-glow  from  all  accidental  interference.  The  sky  was  transparent  and 
cloudlesa  After  sunset  came  the  bluish-white  arc.  At  about  22  minutes  after 
sunset  the  condition  was  as  follows  : — Orange  ordinary  glow  in  S.W.,  near 
horizon  ;  above  this  a  greenish-bluish  white  arc,  then  a  beautifrd  yellow  band  ;  then 
up  to  the  zenith  a  very  beautiful  lUac  tint.  AU  these  colomrs  were  of  extr^ne  soft- 
ness, and  though  not  so  striking  as  in  some  of  the  sunsets  in  December,  in  point  of 
beauty  they  were  quite  unsurpassable,  and  of  superb  magnificence  in  their  further 
progress.  The  pink,  piu^ple,  or  lilac,  now  retired  in  the  most  steady  and  regular 
manner  towards  the  horizon,  and  were  visible  to  the  end ;  35  minutes  after  sunset  the 
arc  was  formed  of  the  inner  part,  which  from  steel-blue  had  gone  through  olive-green 


ON   THE  UNUSUAL  TWILIGHT   GLOWS.  1C7 

to  yellow,  the  middle,  yellow,  and  the  outer,  purple.  Through  the  fringe  of  this, 
Venufl  shone  beautifully.  The  horizon  (about  a  quarter  of  the  circle)  was  deep  yellow. 
The  purple  part  being  the  smallest  was  flooded,  except  at  the  edge,  by  the  orange 
light,  which  shone  in  a  grand  arc  for  a  long  time  with  great  splendour,  casting 
shadows.  In  about  54  minutes  the  primary  glow  was  gone,  having  sunk  in  a  deep 
red  band.  The  eastern  sky  during  the  first  part  of  the  display  was  a  glorious  deep 
blue,  then  very  dark  purple-blue,  and  lastly  only  illumined  by  the  silver  moon. 
The  secondary  glow  was  very  visible,  as  the  thinnest  pink  or  lilac  film,  1  hour  after 
sunset.  It  disappeared  on  the  horizon  about  1  hr.  20  mins.  after  sunset.  The  sky 
streaks  were  less  distinct  than  usual 

"  On  January  11,  the  simrise  was  not  so  fine,  but  the  sunset  (at  Cannes)  gave 
magnificent  e£Gects.  About  22  minutes  after  sunset  the  ulterior  margin  (well-mai'ked) 
of  the  primary  passed  overhead,  leaving  the  east  deep  azure.  As  the  green  gave 
way  to  the  yellow,  the  yeUow  to  pink  and  violet,  and  the  final  deep  red  band  shone 
out  by  itself  from  above  the  Esterel  Hills,  the  most  enchanting  effects  succeeded  each 
other  in  slow  and  regular  order.  Last  red,  50  minutes ;  secondary  glow  30°  above 
the  west  horizon  at  65  minutes  past  sunset,  but  had  been  very  apparent  up  to  and 
beyond  the  zenith  while  the  primary  was  still  bright,  its  first  effect  being  a  curious 
discoloration  of  the  eastern  sky.  At  70  minutes,  very  fine,  dull  red,  in  west ;  just 
disappearing  behind  hills  82  minutes  after  sunset.  The  glows  were  seen  on  the 
following  days,  and  in  travelling  through  France  on  the  14th,  15th,  and  16th." 

Prof.  O.  N.  Stoddakd/*  of  Wooster,  Ohio,  writes  as  follows  respecting  the  sunset 
phenomena  at  that  place : — 

"  The  main  features  of  the  exhibition  here  have  been  the  crimson  glow—  the 
first  and  after-glow  with  other  accompanying  colours,  closely  corresponding  with 
those  in  England  and  the  continent  of  Europe.  I  have  on  record  seven  cases,  which 
were  nearly  all  that  the  weather  would  permit  one  to  see.  These  occurred  on 
November  27,  December  9,  10,  25,  28,  and  January  13  and  17.  The  first  and  second 
glows  have  extended  in  two  or  three  instances,  though  faintly,  to  the  zenith,  and  the 
first  has  occasionally  been  reflected  on  the  eastern  sky.  On  December  28,  the  most 
brilliant  exhibition  in  the  series,  an  arc  was  formed  in  the  east,  the  colours  red  and 
yeUowish-green,  very  soft,  and  much  blended.  The  crimson  glow  on  the  sky  flooded 
the  western  sides  of  buildings  with  an  unearthly  light,  and  cast  faint  shadows  across 
the  snow.  The  appearance  of  the  after-glow,  when  the  sun  had  reached  a  certain 
angle,  fiavours  the  view  that  it  is  a  reflection  of  the  first.  K  this  be  true,  it  is  not 
necessary  to  admit  so  great  an  elevation  of  the  reflecting  matter  above  the  earth.  .  . 
The  glow  has  been  seen  without  the  slightest  trace  of  cirrus  clouds  behind  it.  Three 
times  faint  ribbon-like  stripes  of  cirri  appeared  in  the  first  glow,  but  in  the  second 
the  gorgeous  crimson  has  generally  been  projected  against  the  clear  blue  sky." 

*  'Nature,'  vol.  xxix.  (1884),  p.  355. 
z  2 


168  THE   HON.  ROLLO   RUSSELL 

Prof.  E.  Divers,  of  Japan,  says,*  in  a  letter  dated  December  12,  1883  : — "  On 
some  days  there  is  round  the  sun,  even  whUe  it  is  still  high,  a  considerable  area 
of  silvery  glare,  40°  to  50°  in  diameter,  and  bordered  by  a  lurid  reddish-brown  or 
purplish-brown  halo.  A  similar  lurid  turbidity  lies  on  the  horizon,  and  as  the  sun 
descends  the  halo  blends  with  this  below,  while  above  the  sim  it  attenuates  and 
disappears,  the  silvery  glare  remaining  undiminished.  When  the  sun  sets  there  is 
stiU  a  nearly  circular  area  of  this  intense  glare,  with  a  diameter  of  about  12°,  On 
other  days  there  is,  before  sunset  only,  a  thin  silvery  light  round  the  sun,  diffusing 
away  from  it,  and  only  about  and  after  the  setting  is  the  more  defined  area  of  strong 
light  strikingly  visible,  and  on  these  days  the  horizon  also  shows  little  of  the  dull 
redness  mentioned  above.  Besides  the  above-mentioned  peculiarities  the  sun 
preserves  its  whiteness  much  more  than  usual,  so  as  to  be  only  golden-orange  when 
setting.  Now  follow  the  more  remarkable  phenomena.  The  white  glare,  or  patch 
of  silvery  light,  gradually  sets,  spreading  out  along  the  horizon  as  it  does  so,  and 
passing  through  the  sunset  colours  until  little  more  than  a  red  line  one  or  two 
degrees  deep  remains.  This  happens  at  about  20  minutes  after  sunset.  At  this 
moment,  on  the  grey  curtain  of  twilight  appears  a  white  luminosity,  which  rapidly 
intensifies  over  the  sunset  and  shades  away  over  almost  half  the  visible  hemisphere. 
The  brightness  over  the  sunset  becomes  vividly  brilliant,  and  at  the  same  time 
delicately  coloured.  Over  a  somewhat  depressed  circular  area,  about  12°  high  and 
15°  broad,  it  assumes  a  pale  green  tint.  Above  this  comes  an  equally  dazzling  pale 
yellow-orange,  and  again  above  this  a  soft  rose  colom*  melts  away  to  the  zenith.  The 
revival  of  the  light,  or  return  from  commencing  twilight,  is  peculiarly  striking. 
Buildings  become  brilliantly  illuminated,  and  strong  shadows  are  cast.  All  this 
out-glow  occurs  in  no  more  than  5  minutes,  and  then  continues  for  about  a 
quarter  of  an  hour ;  but  the  brilliancy  gradually  contracts  in  area  and  sets  with  a 
magnificent  display  of  sunset  colours,  reaching  about  120°  round  the  horizon,  until, 
by  50  minutes  aft)er  sunset,  this  light  also  has  gone  down  to  a  red  line  of  about 
2°  elevation.  I  should  not  have  omitted  to  say  that  the  green  light  passes  to 
yellow. 

*'  By  this  time  night  has  fairly  well  come  in  the  eastern  half  of  the  heavens,  but 
already  another  but  more  delicate  silvery  whitening  begins  to  show  itself  on  the 
western  curtain ;  and  this  also  diffuses  very  rapidly  up  to  the  zenith  and  round  to 
north  and  south.  It  also  then  goes  through  a  process  of  contracting,  intensifying  to 
considerable  brightness,  and  gradually  passing  through  the  sunset  colours.  Night  is 
now  full — with  or  without  moonlight,  according  to  date — and  from  the  west,  or 
rather  from  a  point  well  to  the  north  of  it,  spreads  a  delicate  but  brilliant  light, 
having  an  almost  perfect  resemblance  to  the  bimiing  of  a  vast  distant  city.  The 
last  crimson  light  of  this  reflection  does  not  disappear  till  an  hour  and  a  half  after 


sunset." 


*  *Natare;  vol.  xx\x.  (1884),  p»  285. 


ON   THE  UNUSUAL  TWILIGHT   GLOWS.  169 

Herr  J.  Baader  remarks*  as  follows,  respecting  a  morning  twilight  at  Marburg, 
in  Steiermark : — '*  When  I  woke  on  December  1  towards  6  o'clock,  I  observed  at  once, 
through  my  window  towards  the  west,  an  intense  red ;  mountain  and  valley  were 
covered  with  a  marvellous  glow.  The  vineyards  towards  north  and  east,  the 
Matzelgebirge,  south  and  north-west,  the  snow-covered  hills  of  Bacheon  and  Posruck, 
all  was,  including  the  whole  sky,  a  sea  of  fire,  the  f<^  in  the  valleys  like  molten 
metal.  About  6.45,  on  going  out  I  saw,  to  my  great  astonishment,  in  the  E.N.E,  an 
arc  spanning  the  sky,  which  was  yellowish  and  in  parts  pure  blue,  up  to  about  20^ 
The  boundary  of  the  coloured  space  was  sharply  marked  off  from  the  blue  firmament, 
and  moved  with  great  speed  towards  W.S.W.,  although  there  was  hardly  a  light 
current  of  air.  In  a  short  time  nearly  the  whole  sky  up  to  the  zenith  was  free 
from  the  phenomenon — only  in  the  far  west  a  sharply  defined  arc  appeared  for  a 
short  time." 

M,  DuFOUR,  in  his  pamphlet,t  states  the  following  facts  regarding  the  twilight 
glows  as  seen  at  Merges,  in  Switzerland  : — "  They  were  first  noticed  in  Switzerland 
on  November  26 ;  they  diminished  considerably  at  the  beginning  of  December, 
increased  greatly  at  the  end  of  December,  and  were  remarkable  during  the  whole  of 
January.  They  diminished  dining  February,  but  did  not  altc^ther  vanish  ;  till  the 
end  of  1884,  when  the  weather  was  favourable,  the  sky  was  illuminated  in  the 
morning  and  evening  as  by  an  aurora  borealis. 

"  On  January  10,  1884,  the  redness  began  to  appear  at  6  a.m. ;  at  6.30  the  glow 
was  in  all  its  splendoiu* ;  at  6.45  it  began  to  diminish  ;  at  7.5  there  was  a  green  zone 
above  the  mountains,  red  higher  up ;  at  7.15  the  zone  near  the  horizon  was  livid 
green,  the  red  above  it ;  at  7.20  there  was  no  appreciable  redness. 

**  In  the  evening,  at  5  p  jn.,  the  sky  was  yellow";  at  5.6  the  red  was  conspicuous ; 
at  5.40  shadows  were  cast ;  at  6.15  the  redness  disappeared. 

**0n  January  11,  at  5  p.m.,  the  sky  was  yellow ;  at  5.23  aU  the  horizon  was 
coloured  red,  even  in  the  east ;  at  5.25  there  was  a  carmine  zone  in  the  west ;  at  5.36 
the  red  became  very  intense  in  the  west,  in  a  sector  of  which  the  sun  seemed  to 
occupy  the  centre ;  at  5.45  the  Alps  lost  their  red  colour,  but  there  was  intense  glow 
in  the  west ;  at  6.16  the  last  glow  disappeared." 

Capt.  DE  Bmto  Capello  sent  a  report,  published  in  the  *  Standard '  of  December 
26,  1883,  as' follows: — 

"  Captain  Capello,  of  the  Lisbon  Observatory,  has  sent  us  a  succinct  account  of 
the  late  crepuscular  phenomena  of  the  rising  and  setting  of  the  sun.  In  the  first 
place,  he  remarks  that  they  have  been  seen  in  feebler  degree  from  October  the  15th 

*  *  Me*.  Zeitschrift,'  yol.  i.  (1884),  p.  162. 

t  *  Bibliofch^qae  Uaivei-selie,  Geneva,  Archives  dee  Sciences  Physique  etNatui-eUes,' Tome  XI II. — 
Pebraary  15,  1885. 


170  THE   HON.  ROLLO   RUSSELL 

to  the  23rd  or  24th  of  that  month,  showing  themselves  in  a  region  or  segment  of 
parabolic  form  in  the  west-south-west,  the  vertex  inclining  towards  the  north-west.' 
This  region  was  red*orange  coloured  close  to  the  horizon ;  following  this  was  a  rose 
tint,  more  or  less  faint,  and  again  an  elongated  region  of  very  delicate  pearl-white. 
The  white  region  appeared  to  be  formed  of  very  fine  cirrus  and  cirro-stratus,  like 
skeins  of  white  silk ;  the  cirrus  was  not  noticed  before  the  setting  of  the  sun, 
neither  had  the  solar  halo  been  seen  which  is  always  produced  with  the  cirrus  xmder 
normal  conditions.  According  as  this  region  moved  down  towards  the  horizon, 
the  white  light  lost  much  in  intensity,  and  disappeared,  leaving,  as  in  ordinary 
circiunstances,  a  red-orange  band  close  to  the  horizon.  The  red  coloration  elevated 
itself  sometimes  to  the  height  of  30°  to  the  west-south-west,  and  was  seen  an  hour 
after  sunset.  The  18th  October  seems  to  have  been  the  maximum  of  these 
phenomena. 

"  In  the  last  days  of  November,  and  in  the  early  days  of  December,  these 
phenomena  were  observed  in  much  greater  intensity  on  some  days,  both  at  the  rising 
and  at  the  setting  of  the  sun.  Over  and  around  the  region  of  very  vivid  pearl-white, 
the  colours  of  the  twilight,  very  bright  and  exaggerated,  the  crepuscular  and  anti- 
crepuscular  arcs,  which,  under  normal  conditions,  are  arcs  of  a  circle,  have  shown  them- 
selves in  parabolic  form.  The  redness  of  the  sky  (red  and  red-violet)  showed  itself 
sometimes  for  two  hours  after  sunset,  and  spread  itself  in  very  grand  force  to  60°  and 
70°  of  height.  The  duration  of  the  coloration  of  the  sky  is  most  considerable  at 
elevated  points.  Thus,  at  the  meteorological  station  of  Serra  da  EstreUa,  1441 
metres  in  altitude,  they  have  observed  the  redness  of  the  sky  up  to  nine  o'clock  at 
night.  It  should  be  remarked,  also,  that  during  all  these  days  the  sun  was  encircled 
by  a  region  of  whitish  light,  fringed  with  pale  orange-rose  colour.  This  region  never 
appeared  circular;  one  could  not  well  define  the  figure  it  presented,  as  it  had 
irregular  borders,  something  like  the  corona  of  the  sun  in  total  eclipses.  In  the  first 
days  of  December  (1st  and  3rd)  these  crepuscular  phenomena  showed  themselves  with 
greater  intensity,  and  on  the  3rd  and  4th  there  was,  at  4.45  p.m.  Lisbon  mean  time,  Bome 
minutes  after  the  actual  setting,  on  the  side  opposite  to  the  sun  (east-north-east),  a 
segment  which  elevated  itself  from  the  horizon  in  parabolic  form  inclined  towards  the 
north.  On  the  side  of  the  west-south-west,  where  the  sun  went  down,  there  was 
seen  another  much  larger  segment,  affecting  also  the  parabolic  form,  with  the  red, 
orange,  and  pearl-white  colours,  at  first  feeble,  but  augmenting  rapidly  in  intensity. 
After  a  little  while,  towards  4.55,  the  pearl-white  region  showed  itself  silvery,  and 
with  the  greatest  splendour,  the  other  colours  preserving  nearly  the  same  relative 
positions,  only  between  the  white  and  the  orange  a  band  of  very  clear  green  showed 
itself  Then,  at  4.58,  there  began  to  appear  rose  and  clear  violet  colour  encircling 
the  white ;  and  at  5  p.m.  the  rose  elevated  itself  to  the  height  of  50°.  All  the 
eastern  side  of  the  town  was  illuminated  in  a  peculiar  manner,  and  this  illumination 
lasted  for  about  12  minutes.     This  rose  tint,   more  or  less  violet,  went  up  to  the 


ON  TEE  UNUSUAL  TWILIGHT   GLOWS.  171 

north,  during  which,  in  the  south,  one  saw  a  broad  band  of  orange-yellow.  On  the 
east  side,  the  pale  yellow  at  4.55  p.m.  was  augmented  in  intensity,  and  showed  itself 
very  high  (maximum  elevation) ;  the  other  colours  presented  themselves  nearly  in  the 
same  relative  positions.  After  5  p.m.  all  these  colours  of  the  east-north-east 
decreased  rapidly  in  extent  as  well  as  in  intensity,  and  in  a  little  time  (5.5  p.m.) 
there  remained  only  a  violet  arc  from  north-east  to  south-east.  Towards  5.3  p.m. 
the  pearl-white  region  (west-south-west)  sank  little  by  little  in  the  direction  where 
the  sun  had  set,  losing  its  brilliancy,  whilst  above,  a  new  region  of  yeUowish-pinfc 
rose  to  75^,  extending  from  north  to  south.  The  sky  at  the  zenith  was  then  of  a 
deep  azure,  almost  black,  and  the  moon  showed  itself  of  a  green  colour.  A  little 
later,  5.8  p.m.,  the  exterior  rose  region  presented  itself  streaked  by  different  blue 
rays,  which  diverged  from  the  point  where  the  sun  was  below  the  horizon.  The 
phenomenon  was  very  like  aurora  bore^lis.  Little  by  little  the  colours  chauged ;  the 
white  region  became  very  narrow,  and,  sinking  towards  the  horizon,  It  assumed,  at 
5.15  p.m.,  a  red-orange,  bordered  with  gold.  Soon  after,  the  phenomenon  ceased. 
At  5.18  to  5.20  p.m.  the  red  coloration,  more  or  less  violet,  extended  itself  rapidly  all 
over  the  horizon  from  north  to  south,  reaching,  on  the  west,  to  60°  of  elevation  ;  and 
this  red  coloration  maintained  itself  up  to  6.30  p.m.,  that  is,  for  an  hour  and  forty 
minutes  after  the  setting  of  the  sun.  Since  the  3rd  instant  these  phenomena  have 
lost  much  in  intensity,  bqt  all  the  characteristic  points  have  been  preserved — for 
example,  the  parabolic  form  of  the  crepuscular  and  anti-crepuscular  arcs,  and  the 
white  and  coloured  spaces.  On  the  12th,  the  redness  of  th0  sky  was  observed  up  to 
6.20  p.m.  During  the  whole  period  the  magnetic  curves  have  presented  nothing 
extraordinary,  apart  from  some  little  perturbations  very  common  during  the  maxi« 
mum  of  solar  spots." 

Professor  von  Helmholtz*  wrote  from  Berlin  on  December  1  : — "  The  pheno- 
menon called  cloud-glow  in  your  last  numbers,  was  seen  also  at  Berlin  on  the  three 
evenings  of  November  28,  29,  and  30.  As  far  as  1  qould  observe  the  sky,  the  details 
were  almost  the  same  as  your  correspondents  describe  them  :  a  greenish  sunset  at 
3.50 ;  an  unusually  bright  red  sky  with  flashes  of  light  starting  from  south-west. 
An  interesting  physiological  phenomenon,  which  we  call  '  Contrast/arben,'  was  there 
beautifully  illustrated  by  some  clouds,  no  longer  reached  by  direct  sunlight ;  they 
looked  intensely  green  on  the  red  sky.  At  4.30  the  streets  were  lighted  by  a 
peculiarly  pale  glare,  as  if  seen  through  a  yellow  glass.  Then  darkness  followed 
and  the  stars  became  visible.  But  half  an  hour  afterwards,  at  5  o'clock,  the  western 
fiky  was  again  coloured  by  a  pink  or  crimson  glow.  Persons  who  were  not  quite 
sure  about  its  direction  mistook  it  for  an  aurora ;  others  spoke  of  a  great  fire  in 
the  neighbourhood.     .     .     At  6  o'clock  all  was  over." 

•  'Natui-e,'  vol.  xxix.  (1883),  p.  130. 


172  THE   HON.  EOLLO  BUSSELL 

Mr.  Gerard  Hopkins,  of  Stonyliurat  College,*  notes  the  following  difference 
between  ordinary  sunsets  and  the  displays  of  1883  : — 

"(1).  They  differ  in  their  time  and  in  the  place  of  the  sky  where  they 
appear. 

"  (2).  They  differ  in  their  periodic  action  or  behaviour. 

"  (3).  They  differ  in  the  nature  of  the  glow,  which  is  both  intense  and 
lustreless. 

"  (4).  They  differ  in  the  regularity  of  their  colouring.  Four  colours  in  particular 
have  been  noticeable,  orange  lowest  and  nearest  the  sundown;  above  this  and 
broader,  green ;  above  this,  and  broader  still,  a  variable  red,  ending  in  being  crimson  ; 
above  this,  a  faint  lUac.  The  lilac  disappears,  the  green  deepens,  spreads,  and 
encroaches  on  the  orange,  and  the  red  deepens,  spreads,  and  encroaches  on  the  green, 
till  at  last  one  red,  varying  downwards  fi-om  crimson  to  scarlet  or  orange,  fills  the 
west  and  south. 

*'  (5).  They  differ  in  the  colours  themselves,  which  are  impure  and  not  of  the 
spectrum. 

"  (6).  They  differ  in  the  texture  of  the  coloured  surfaces,  which  are  neither 
distinct  clouds  of  recognised  make,  nor  yet  translucent  media." 

The  above  is  merely  an  abstract  of  Mr.  Hopkins's  letter,  to  which  he  subjoins 
a  very  lucid  description  of  the  sunset  of  December  16,  1883. 

Herr  Dr.  E.  von  Rebeur-Paschwitz  v«Tote,t  on  December  the  19th,  from 
'Berlin: — "Yesterday,  December  18,  the  twilight  phenomenon,  though  much  less 
grand,  was  very  well  seen.  Soon  after  sunset,  the  western  sky,  which  seemed  to  be 
covered  with  a  very  fine  vapour  stratum,  but  otherwise  was  cloudless,  assumed  a 
greenish-white  colour.  At  about  4.15,  at  some  altitude  above  the  horizon,  the 
first  reddish  sheen  was  observed ;  and  it  soon  expanded  over  a  larger  oval  space,  and 
increased  in  intensity.  This  space  filled  with  red  light  did  not  reach  to  the  horizon, 
but  was  separated  from  it  by  a  narrow  streak  of  white  of  intense  brightness.  At 
last  the  whole  horizon  in  the  west  shone  with  a  beautiful  orange  colour.  Yesterday, 
as  on  the  17th,  a  fine  striation  of  the  bright  part  of  the  sky  was  noticed.  Broad 
streaks,  inclined  to  the  horizon,  and  nearly  parallel,  covered  the  western  sky. 
The  inclination  of  the  streaks  was  variable ;  on  the  19th  they  were  nearly  parallel  to 
the  horizon.  This  striation  of  the  sky  has  been  seen  on  three  successive  evenings, 
and  also  on  the  first  days  of  December.  Through  an  opera-glass  the  streaks  looked 
like  fine  clouds,  but  could  hardly  be  described  as  cirrus.  At  4.53  the  red  glow  was 
all  but  gone ;  at  5.2  there  was  another  weaker  redness,  more  towards  the  north  than 

*  'Nature/  vol.  xxix.  (1884),  p.  222. 

t  *  Met.  Zeitsohrift,'  vol.  i.  (1884),  p.  160. 


ON  THE  UNUSUAL  TWILIGHT  GLOWS.  173 

before ;  at  5.5  a  sudden  renewal  of  the  red  glow  ;  at  5.20  there  was  a  diminution  ; 
and  at  5.30  the  glow  had  disappeared." 

Mr.  E.  L.  Layard*  wrote  as  follows,  on  January  6,  1884,  from  Noumea,  New 
Caledonia  : — '*  As  soon  as  the  suns  disc  has  disappeared,  a  glow  comes  up  from  the 
west  like  that  of  whit^-hot  steel,  reddening  somewhat  as  it  mounts  to  the  zenith,  but 
changing  the  while  to  blue.  From  the  zenith  it  passes  into  the  most  exquisite  green, 
deepening  as  it  loses  itself  in  the  east.  As  the  sun  sinks  lower  and  lower,  the  red 
tints  overpower  the  white-hot  steel  tints,  and  the  blue  of  the  zenith  those  of  the 
green.  At  7  p.m.,  or  a  little  after,  nearly  the  entire  western  half  of  the  horizon  has 
changed  to  a  fiery  crimson :  as  time  goes  on,  the  northern  and  southern  areas  lose 
their  glory,  and  the  greys  of  night  contract,  from  the  northern  end  first,  most  rapidly ; 
the  east  is  of  the  normal  grey.  The  south  now  closes  in,  and  presently,  about  8  p.m., 
there  is  only  a  glare  in  the  sky,  just  over  the  sun's  path,  as  of  a  distant  conflagration, 
till  the  fire  in  the  west  dies  out.  I  have  been  attempting  to  describe  one  of  our 
cloudless  evenings,  of  which  we  have  had  only  too  many,  having  just  come  through 
a  fearful  drought  that  has  lasted  all  this  while ;  but  who  shall  paint  the  glory  of 
the  heavens  when  flecked  with  clouds  ? — burnished  gold,  copper,  brass,  silver,  such  as 
Turner  in  his  wildest  dreams  never  saw,  and  of  such  fantastic  forms  I " 

M.  de  MoNTESSUS,  writing,  "Sur  les  lueui-s  cr^pusculaires  observ^es  k  San 
Salvador  (Am6rique  centrale),"  t  under  date  February  9,  1884,  says  : — 

"  The  remarkable  sunsets  have  been  seen  here  since  the  last  days  of  November, 
1883.  About  half  an  hour  after  sunset,  and  an  hour  before  sunrise,  the  horizon  is 
gradually  illuminated  with  a  magnificent  coppery -red  tint,  very  constant  in  colour, 
very  intense,  and  lasting  on  the  average  20  to  25  minutes.  The  phenomenon  is  not 
produced  except  in  a  cloudless  sky.  If  there  are  a  few  strati  on  the  horizon  in  the 
evening  it  is  not  produced ;  in  the  morning  it  may  occiu:  with  a  few  strati,  and 
especially  with  high  cirri.  The  illumination  extends,  horizontally,  at  least  70^  to  the 
right  and  left  of  a  plane  passing  vertically  through  the  sun  and  reaches  up  nearly  to 
the  zenith ;  consequently,  nearly  half  the  hemisphere  is  filled  with  the  splendid  red 
glow.  The  moon,  when  circumstances  allowed  of  it — that  is,  when  her  altitude  did 
not  exceed  15°,  was  coloured  a  magnificent  emerald -green,  and  it  was  extremely 
beautiful  to  see  it  at  the  epoch  of  grey  light  {lumiere  cendree),  when  its  disc  was  of  a 
pale  green,  with  its  crescent  horn  deep  green  in  the  midst  of  an  immense  crimson 
curtain.  Venus  only  was  able  to  penetrate  the  curtain,  and  was  also  green.  Stars 
of  the  first  magnitude  could  not  be  seen  ;  and  those  which  at  a  sufiiciently  great 
altitude,  such  as  the  small  comet,  were  clearly  distinguishable,  were  also  green. 
The  phenomenon   rapidly  acquired  its  maximum  intensity,  which  it  retained  3  or 

*  'Natnre,'  vol.  xxix.  (1884),  p.  461. 
t  '  Comptes  RendnB',  xcviii.  (1884),  pp.  761,  762. 

2  A 


174  THE  HON.  ROLLO  RUSSELL 

4  minutes  only,  and  then  as  rapidly  disappeared,  after  lasting  altogether  about  25 
minutes.  I  did  not  at  first  note  down  the  dates  of  the  first  appearances.  There 
were  two  or  three  before  November  30.  Subsequently  they  were — November  30, 
December  1,  2 ;  January  3,  4,  7,  17,  18,  21,  22,  23,  25,  26,  27,  28,  29,  30,  31 ; 
February  4,  6,  7.  Yesterday  the  overcast  sky  allowed  us  to  see  it  only  at  intervals 
for  a  few  minutes.  At  Panama  some  of  the  old  men  report  having  seen  similar  glows 
before,  but  they  could  not  recollect  the  precise  year.  The  magnetic  needle  was 
quiet.  There  was  nothing  unusual  recorded  by  the  meteorological  instruments.  The 
centre  of  the  glow  seemed  to  be  in  the  vertical  plane  of  the  sun.  The  zodiacal 
light  was  absolutely  annihilated." 

Mr.  John  Ballot,  of  Roefontein  Wakkerstroom,  Transvaal,  S.  Africa,  in  a  letter 
dated  March  10,  1884,*  says: — "The  exact  date  on  which  the  glow  made  its  first 
appearance  in  this  country,  I  am  not  in  a  position  to  give.  It  is,  however,  certain 
that  it  was  observed  as  early  as  September  5,  1883.  From  about  September  7,  it 
had  already  become  a  very  noted  peculiarity  after  sunset,  even  to  the  most  imob- 
servant.  The  colour  of  the  light  was  at  first  of  a  sickly  greenish-yellow,  but  deepened 
into  a  copperish-red  as  the  evening  advanced  ;  the  light  was  strong  enough  to  cast  a 
deep  shadow  against  a  wall  or  anything  else,  if  an  object  was  held  close  to  it.  •  .  . 
The  greenish  tint  of  this  glow  seemed  to  me  to  prove  that  it  was  caused  by  light 
reflected  and  refracted  by  an  atmospliere  heavily  charged  with  water  vapour." 

Therefore  Mr.  Ballot  predicted  heavy  rains  and  the  disappearance  of  the 
glows.  The  rains  came,  but  the  glows,  nevertheless,  continued  to  March  10,  the 
date  of  writing. 

"  The  glow  remained  visible  almost  every  evening  whenever  there  was  suflEicient 
clear  sky  to  reveal  it.  .  .  .  One  evening  it  would  attain  to  a  greater  altitude 
than  another,  or  be  more  brilliant.  As  time  went  on,  the  general  colour  of  the  light 
seemed  to  deepen  to  a  darker  copperish-red  or  muddy-orange,  with  a  shade  of  rosiness 
diffused  in  its  remoter  parts.  .  .  .  The  general  tint  is  cei-tainly  much  deeper 
than  it  was  at  first.  The  conditions  most  favourable  to  a  grand  display  and  cloud 
effect  are  a  clear  sky  towards  the  time  of  sunset,  with  a  few  detached  clouds  floating 
about,  and  a  slightly  cloud-streaked  horizon.  When  such  has  been  the  case  I  have 
frequently  observed  innumerable  rays  of  the  beautiful  glow  darting  out  from  behind 
the  cloudy  horizon  to  great  altitudes,  and  in  every  direction,  the  intervals  between  the 
rays  being  comparatively  dark.  ,  .  .  That  the  reflecting  medium  producing  the 
glow  is  situated  at  greater  altitudes  than  the  general  cloud  layer  is  proved  by  the  fact 
that  these  cloud  masses  appear  quite  black  when  projected  against  the  rosy  back- 
ground. The  thinner  edges  of  such  clouds  frequently  acquire  a  dark  olive-green 
colour  ;  while  at  other  times  I  have  seen  them  slightly  rose-coloured  by  the  reflection 

*  '  English  Mechanic/  May  2, 1884,  p.  185. 


ON   THE   UNUSUAL  TWILIGHT   GLOWS.  175 

of  the  glow,  the  cloud  itself  remaming  a  dark  mass.  .  .  A  few  concluding  remarks 
will  be  devoted  to  the  order  in  which  the  glow  is  generally  formed.  A  rough  diagram 
is  annexed,  simply  to  enable  the  reader  better  to  understand  the  description. 

Fig.  14. 


"h  h,  the  horizon;  A  A^  fading  portion  of  ordinary  twilight,  with  the  point  of  sunset  heavily  shaded;  B  B,  the 
brownish  belt  of  glow  due  to  denser  lower  strata;  C  C,  vacant  spa^ce  between,  the  two  glows^  above 
which  the  second  glow  begins  to  form;  D,  the  bluish-white  glare;  E  E,  the  copperish-red  gloxo; 
K,  where  the  purplish  tint  is  brightest,  fading  into  violet  at  j. 

"  Soon  after  sunset,  the  usual  twilight  appears,  which  remains  visible  for  a  short 
while  ;  as  it  gradually  contracts  and  fades,  everything  seems  to  be  settling  down  for 
the  approaching  darkness.     The  rosy  glow  over  the  point  of  sunset  rapidly  contracts, 
only  a  thin  rim  of  red  remains  visible  on  each  side,  with  a  small  arc  of  red  marking 
the  point  of  sunset.     The  observer  will  now  begin  to  notice  a  peculiar  bluish-white 
glare  forming  a  few  degrees   above  the  arc  of  red,  and  extending  some  distance 
upwards.     The  white  glare  increases  a  little,  when  again  a  slight  reddish  tint  makes 
an  appearance  round  about  the  white.     When  once  commenced,  the  red  light  spreads 
rapidly  upwards  and  in  a  horizontal  direction,  but  does  not  seem  to  make  much 
progress  towards  the  horizon.     The  fading  rim  of  the  first  twilight  forms  itself  into  a 
long,  narrow,  brownish  belt,  stretching  along  the  horizon,  caused,  no  doubt,  by  the 
denser  layers  of  haze  and  vapour  lower  down.     Immediately  above  this  belt,  and  just 
below  the  bluish-white  glare,  there  remains  an  apparent  blank ;  this  blank  is  but 
slowly  filled  up  by  the  new  glow.     It  seems  as  if  the  reflecting  media  in  that  belt  are 
below  the  line  of  reflection  as  yet.     As  the  glow  spreads  outwards  above  the  white 
glare,  it  seems  to  acquire  a  strong  tinge  of  purple,  which  gradually  fades  into  a  violet 
near  the   borders  of  the  spreading  luminosity.     The   arc  of  bluish-white  gradually 
gives  place  to  a  very  strong  copperish  glare.     But  as  the  evening  advances  the  light 
assumes  a  more  uniform  colour.     The  purple  and  violet  entirely  disappear,  and  the 
enttt^  luminosity  contracts  towards  the  point  of  sunset,  where  it  finally  disappears  at 
from  one  to  one-and-a-half  hours  after  sunset.    .    .    .    The  glow  generally  has  a  much 
greater  extension  round  the    southern  horizon  than  round  the  north-western.      It 
fi-equently  extends  more  than  90°  round  the  southern,  whereas  it  seldom  exceeds  60° 
round   the   northern.     Taking   everything  into   consideration,    there   seems   to   me 

2  A  2 


176  THE   HON.   ROLTiO   RUSSELL 

decided  proof,  from  these  observations,  that  aqueous  vapour  plays  an  important 
part  in  producing  the  after-glow." 

Again,  he  says*  that  during  March  and  April  peculiarities  were  strongly  devdoped 
which  had  not  been  noticed  before: — "  All  throughout  March  I  frequently  observed  it 
in  broad  daylight,  especially  one  or  two  hours  before  sunset*  But  as  the  sky  was 
generally  covered  with  broken  cloud  I  thought  it  peculiarly  favourable  to  reveal  the 
illuminated  dust  haze  beyond,  the  sun  himself  being  covered  from  view  at  times. 
April,  however,  brought  a  clearer  sky,  yet  the  glow  forms  an  easily-detected  daylight 
phenomenon.  About  3  minutes  after  sunrise  it  is  plainly  seen  on  each  side  and  along 
the  horizon,  even  above  the  sun.  The  sides  and  lower  portion  of  glow  ai^e  of  a 
brownish-grey,  while  above,  or  preceding  the  sun,  it  is  wbitish-grey.  The  sun  with 
the  surrounding  glow  resembles  in  shape  a  huge  comet,  of  which  our  luminary  forms 
the  gigantic  nucleus,  the  head  and  part  of  the  tail  alone  having  risen  above  the 
horizon.  This  glow  gradually  contracts  about  the  sun,  being  always  much  elongated 
on  the  side  nearest  the  horizon.  About  midday  a  faint  white  glare  alone  is  visible  ; 
but  towards  afternoon  the  same  phenomenon  as  at  sunrise  occurs,  only  reversed  iu 
direction.  Some  moments  after  sunset  the  bluish -white  heart-shaped  glare  forms 
itself;  on  each  side,  a  dull  brownish-red  arm  of  light  is  seen  stretching  northward  and 
southward  along  the  horizon.  Some  minutes  later,  and  just  about  when  the  heart- 
shaped  bluish-white  glare  attains  its  brightest,  an  arc  of  light  is  formed  in  the  eastern 
sky,  resting  on  the  band  of  light  or  band  of  glow  which  now  surrounds  the  horizon. 
This  arc  resembles  in  shape  a  small  segment  of  a  rainbow,  and  rises  to  an  altitude  of 
about  50°  to  60°.  Inside  there  seems  to  be  a  blank  or  want  of  light.  Meanwhile 
the  secondary  glow  is  beginning  to  form  in  the  west  at  an  altitude  of  about  40°,  and 
just  over  and  round  about  the  bluish- white  glare.  A  few  minutes  later  and  the  whole 
sky  seems  to  show  a  feeble  illumination,  while  the  arc  of  light  in  the  east  rapidly  disap- 
pears. The  secondary  glow  has  now  reached  a  deep  rosy-red  tint,  as  before  described ; 
at  first  seemingly  floating  some  degrees  above  the  horizon,  but  gradually  sinking  lower 
and  acquiring  more  uniformity  of  textura  The  regions  near  the  horizon  pass  through 
bright  yellow  to  dark  orange  very  deep  in  tint.  About  45  minutes  after  sunset  this 
secondary,  and  most  magnificent  glow,  contracts  towards  the  point  of  sunset  and 
settles  on  the  horizon  line.  As  soon  as  this  happens,  the  arms  of  light  and  general 
luminosity  of  the  sky  mentioned  above  entirely  disappear.  Stars  of  smaller  magni- 
tude become  better  defined,  and  the  twinkling  of  the  stars  in  general  seems  to 
become  more  decided.  Everything  settles  in  for  night  and  darkness.  When,  lo  1 
the  seemingly  expiring  glow  in  the  west  is  again  seen  to  increase  ;  about  45°  above  the 
horizon  a  similar  duU  glow  is  forming,  which  increases  in  Uke  manner  as  the  secondary 
glow.  The  pale  glow  over  thehprizon  assumes  a  peculiar  greenish-yellow,  which 
gradually  deepens  into  a  muddy  fiery  red.     A  third  glow  appears,  and  behaves  much 

*  '  English  Mechanic,*  Jane  6,  1884,  p.  296. 


ON  THE   UNUSUAL  TWILIGHT   GLOWS.  177 

the  same  as  the  secondary  glow,  only  its  general  tints  seem  duller.  This  glow  has 
but  little  reflecting  influence  on  the  now  rapidly-darkening  sky,  situated  further 
eastward,  which  produces  a  strange  effect  of  contrast.  It  seems  to  me  that  this 
glow  may  be  caused  by  reflection  from  dust  haze  situated  at  a  greater  altitude 
thaji  the  dust  haze  of  the  secondary  glow.  In  other  words,  there  are  two  layers 
of  dust  floating  in  the  upper  strata  of  the  atmosphere,  but  at  very  different 
altitudes ;  while  in  between  them  there  can  be  but  little  diffused  dust  floating 
about,  hence  the  interval  between  the  glows." 

M.  Pelagaud  writes,  on  AprU  14,  1884,  from  St.  Paul,  Bourbon,  as  follows  : — 
"  NouveUes  observations  d'illuminations  cr^pusculaires  kl'ile  Bourbon.*  Our  twilight 
glows  have  passed  into  a  new  phase,  the  intermittent  phase.  Some  days  they  almost 
entirely  disappear  and  are  represented  only  by  a  slight  phosphorescence ;  then  the 
next  day  they  recur  with  renewed  intensity. 

"  On  April  4,  they  were  admirable  and  as  beautiful  as  ever ;  and  again  on 
AprU  1 1 ;  but  they  did  not  have  the  same  arrangement  as  at  first.  Then  they 
consisted  of  three  large  tricoloured  zones,  which  extended  from  the  west  to  the 
zenith,  and  were  sometimes  separated  from  one  another  by  three  wide  coloured 
bands  of  blue  sky.  Now  they  are  usually  glories  which  shoot  up  in  divergent 
rays  to  50®  or  60°  At  7  or  8  minutes  after  sunset  a  pale  luminous  lilac  spot 
begins  to  be  defined  at  10°  or  12°  above  the  point  where  the  sun  has  disappeared  ; 
its  diameter  may  be  about  15°.  To  the  right  and  left  are  two  smoky  walls  like  the 
smoke  from  a  large  town,  seen  as  a  transparency  against  the  red  horizon  of  the 
setting  Sim.  Then  these  walls  vanish,  the  lUac  spot  disappears ;  and  just  above  it 
there  begins  to  appear,  about  15  minutes  after  sunset,  a  luminous  haze  of  scarlet 
pintle  and  crimson  hue,  and  of  a  discoidal  form,  which  gradually  widens  to  15°  or 
20°,  increasing  in  intensity  of  lustre,  and,  soon  after,  shoots  upwards  the  great 
rays  above-mentioned.  At  the  moment  when  these  rays  appear  the  lower  margins 
of  the  disc  retract,  and  take  the  form  of  an  arc  of  a  circle  resting  on  the  horizon ;  but 
all  the  margins  are  indefinite.  Sometimes  obscure  rays  are  observed  between  the 
bright  ones,  especially  on  the  south  side.  *  All  this  lasts  a  quai-ter  of  an  hour  or 
20  minutes,  and  then  gradually  fades  away  untU,  at  about  6.35  or  6.40,  there  remains 
only  a  yellow  band  on  the  horizon,  which  also  soon  disappears.  I  am  induced  to 
think  that  the  phenomenon  is  electrical.  Cyclones  have  been  unusually  prevalent,  and 
these  exclude  all  hypotheses  as  to  the  suspension  of  fine  particles  in  the  higher 
atmosphere  for  upwards  of  six  months.  On  the  other  hand,  I  have  seen  (once  only, 
it  is  true)  a  roseate  haze  start  from  a  very  high  cirro-stratus." 

Prof,  von  BKZOLD,t  of  Munich,  observes  that : — "  Besides  the  extreme  brilliancy 
and  depth  of  colour  some  other  points  may  be  specified  as  abnormal : — 

•  *  CompteslRendTis,'  xcviii.,  pp.  1301, 1302. 
t  *  ZeiiBcHrift  fur  Meteorologie,'  1884,  p.  72. 


178  THE  HON.  ROLLO  RUSSELL 

1.  "  While,  in  ordinary  conditions,  after  sunset  or  before  sunrise,  an  increase 
of  brightness  is  observed  in  the  neighbourhood  of  the  sun  (near  the  horizon), 
having  the  form  of  a  weakly  illuminated  disc  with  a  spot  above  the  sun  for 
its  centre,  this  appearance  has  lately  been  far  more  striking  than  usual. 

2.  "Immediately  before  sunrise,  or  after  sunset,  the  illumination  of  the  sky, 
particularly  with  a  hazy  atmosphere,  turned  to  a  peculiar  yellow,  often  of  a  sulphur 
colour,  such  as  is  not  seen  in  ordinary  twilights. 

3.  "The  illumination  of  the  whole  sky  was  unusually  diffuse,  so  that  the 
boundary  of  the  so-called  earth  shadow  could  never  be  clearly  recognised. 

4.  "The  first  purple  light,  of  which  the  maximum  appeared  from  30  to  35 
minutes  after  sunset  between  Januaiy  8th  and  1 3th,  was  much  more  extensive 
and  less  well  defined  than  usual.  Whereas  usually  it  appears  as  a  defined  disc 
above  the  bright  yellow  segment,  so  that  its  lower  part  appears  to  be  covered 
by  the  yellow,  and  whereas  it  very  seldom  reaches  to  the  zenith  and  never  beyond 
it,  in  the  recent  twilights  the  greater  part  of  the  sky  was  frequently  flooded 
with  purple  light. 

5.  "  Quite  abnormal,  too,  was  the  extent  and  intensity  of  the  second  purple 
light.  It  reached  its  maximum  about  70  or  80  minutes  after  sunset,  as  in  a 
normal  twilight,  but  was  incomparably  brighter,  and  much  more  strongly  coloured," 

F.  A.  RoLLO  Russell 


PART  IV.,   SECTION  I.  (b). 

Proximate  Physical  Cause  of  the  Unusual  Twilight  Glows 

IN  1883-4, 

By  the  Hon.  Rollo  Russell. 

The  condition  of  atmosphere  most  favourable  to  the  visibility  of  the  complete 
and  undisturbed  fore-glows  and  after-glows  of  1883-4  was  freedom  from  clouds,  and  a 
transparent  lower  air.  Any  haze  of  an  ordinary  kind  in  the  upper  or  lower  air 
greatly  interfered  with  the  characteristic  phenomena.  Also  when  the  unusual 
haze  which  accompanied,  and,  as  we  shall  show,  probably  produced,  these  phenomena, 
was  present  in  sufficient  quantity  to  cause  an  appearance  of  mist  on  the  horizon  and 
to  obscure  the  sun  before  setting  it  was  unfavourable  to  the  observation  of  fine  displays. 

This  latter  condition  prevailed  in  Surrey  on  November  23,  24,  and  25,  1883, 
the  sun  vanishing  in  a  misty  film  of  striae  resembling  indistinct  cirro-stratus. 
The  sunset  on  those  days  was  followed  by  appearances  detailed  in  Section  I.  (a), 


ON  THE   CAUSE    OP   THE   UNUSUAL  TWILIGHT   GLOWS.  179 

pp.  152-178.  The  sun  as  it  sank  into  the  haze  was  peculiarly  white,  but  not  well- 
defined,  being  surrounded  by  a  kind  of  halo  and  having  a  green  light  above  it.  This 
haze  seems  to  have  been  very  similar  to  that  which,  three  months  earlier,  obscured 
the  sim  in  the  tropics  near  the  equator ;  while,  further  from  the  equator,  where  the 
lofty  haze  was  less  dense,  brilliant  after-glows  were  seen.  Several  observers 
in  the  Atlantic,  Indian,  and  Pacific  Oceans,  described  the  sun  as  disappearing  at 
some  altitude  above  the  horizon. 

The  white  haze  described  in  Section  I.  (a),  when  distinctly  visible  as  a  stratum 
at  a  great  altitude,  was  favourable  to  the  production  of  fine  displays,  and  preceded 
the  most  brilliant  and  extensive  after-glows.  At  Honolulu  the  sky  was  seen  to  be 
covered  with  a  very  light  wavy  mist,  and  in  many  parts  of  the  world  a  lofty  striated 
haze  was  seen  previous  to  the  red  illuminations  of  the  sky.  In  England  it  was 
noticed  by  several  observers.  In  Italy,  in  January,  1884,  the  white  gauzy  veil  after 
sunset  was  the  surest  prelude  to  a  display.  In  Europe,  as  stated  in  Section  I.  (a), 
the  stratum  in  fuU  daylight  was  white,  apparently  nearly  motionless,  and  almost 
invariably  arranged  in  parallel  streaks  stretching  from  about  south  or  south-west  to 
north  or  north-east.  It  gave  the  impression  of  lying  at  a  very  great  altitude ;  and 
this  impression  was  strengthened  when  it  was  found  that,  for  more  than  two  months, 
through  all  kinds  of  weather,  it  persistently  preserved  its  peculiar  character  and 
apparent  immobility,  even  when  high  cirrus  clouds  were  moving  rapidly ;  that  after 
sunset  and  long  aft;er  the  highest  clouds  in  the  neighbourhood  had  lost  their  colour,  it 
seemed  to  be  illuminated  by  direct  sunlight ;  that  it  was  accompanied  by  the  appear- 
ance of  a  corona  round  the  sun  during  the  day,  much  better  visible  at  altitudes  of 
10,000  feet  than  lower  down  ;*  that  the  streaks  of  which  it  was  composed  converged 
to  a  radiant  point  much  below  the  horizon,  and  gave  the  impression  of  being  really 
parallel,  and  that  though  the  duration  of  the  morning  and  evening  glows  gradually 
diminished,  the  stratum  did  not,  for  some  months,  reach  a  level  affected  by  the 
currents  of  the  cirrus  region. 

We  may  thus  fairly  conclude  that  a  stratum  of  matter,  not  usually  discover- 
able, was  present  in  the  upper  atmosphere  of  a  great  part  of  the  globe  during  the 
autumn  and  winter  of  1883-4,  that  is,  during  the  period  when  the  remarkable 
glows  were  conspicuous.  The  first  remarkable  sky  colorations  of  long  duration 
were  observed  at  several  places  in  the  Indian  Ocean  on  August  26  and  27,  and 
rapidly  extended  in  various  directions,  but  chiefly  W.  and  S.W.  Lines  drawn  from 
place  to  place  in  the  order  of  dates,  if  prolonged  backwards,  meet  somewhere  near 
the  Strait  of  Sunda,  which  must  therefore  be  taken  to  be  the  place  of  origin  of  the 
cause  of  the  glows.  On  the  same  days  the  ocean  was  covered  to  a  long  distance, 
especially  westward,  with  a  very  fine  dust,  consisting  chiefly  of  pimaice,  floating  lightly 
on  the  surface ;  and  this  fine  dust  was  noticed  to  fall  from  the  sky  as  far  as  1,175 

♦  FoRBL,  in  Switzerland   (*  Comptes '  Rendua,'   xcix.,  p.  423) ;  and  Hetde,  at  Kailong,  Lahoul, 
India  (MS.)  ;  and  Backhouse  (*  Nature,'  Au^st  14,  1884). 


180  THE  HON.  ROLLO   RXTSSELL 

English  miles  west  of  Java  on  A^ugust  28,  and  at  3,754  English  miles  W.N.W.  on 
September  8.  This  also,  by  the  order  of  dates,  showed  an  origin  near  the  Strait  of 
Sunda.  A  whitish  or  yellowish  sky  and  a  blue  or  green  sim  were  seen  on  the  same 
days,  August  26  and  27,  and  first  in  the  neighbourhood  of  the  Strait  of  Sunda ; 
so  that  all  these  phenomena  depended  on  some  agency  at  work  in  that  quarter. 
The  widely-extended-fall  of  dust  from  this  yellowish  sky,  and  the  long-continuance 
of  the  haze  in  the  upper  regions,  make  it  reasonable  to  assume  that  the  lofty  stratum 
consisted  of  exceedingly  fine  dust,  projected  by  some  cause  to  a  height  above  that  of 
the  known  atmospheric  currents. 

The  great  eruption  of  Krakatoa  on  August  26  and  27  appears  to  be  an  adequate 
cause.  And  its  potency  can  hardly  be  doubted  when  w^e  compare  ite  effects  with 
those  of  two  other  years  of  great  volcanic  activity,  namely,  1783  and  1831,  which 
were  distinguished  by  similar  coloured  suns  and  red  after-glows.*  The  redness  of  the 
sun  in  1783,  which  was  more  frequent  than  the  moon-like  appearance,  may  be 
attributed  to  the  density  of  the  volcanic  haze  in  the  lower  and  intermediate  air ;  and 
this  condition  had  its  counterpart  in  1883  in  the  Indian  Ocean,  wherever  the  lower 
as  well  as  the  upper  air  was  unusually  hazy.  The  haze  which  caused  the  blue  sun 
in  the  tropics  did  not  lose  its  properties  as  it  spread  northwards  ;  for  in  Europe  the 
sun  appeared  whiter  than  usual  at  low  altitudes,  the  moon  was  occasionally 
slightly  greenish  during  the  night,  and  the  stars  were  less  yellow  and  more 
green.  As  in  the  tropics,  the  red  after-glows  accompanied  the  red-arresting  or 
blue-sun  haze,  when  not  too  dense.  If  the  influence  of  the  lower  atmosphere 
could  have  been  eliminated,  there  can  be  little  doubt  that  a  greenish  tinge  would 
have  slightly  predominated  in  the  sun  half  an  hour  before  sunset.  In  China,  for 
example,  the  sun  was  seen  green  in  November,  and  the  fiery  sunsets  took  place 
soon  after. 

In  order  to  realize  the  effects  of  absorption  (so-called)  at  heights  beyond  the 
paramount  influence  of  the  lower  air,  let  us  place  ourselves  in  imagination  in  the 
middle  of  the  lofty  dust-stratum,  and  observe  the  appearance  of  the  sun  as  it 
approaches  the  horizon.  When  it  reaches  a  point  at  which  it  is  shining  through  a 
maximum  length  of  the  stratum,  it  must  appear  greenish  or  bluish  ;t  then,  as  it  sinks 
lower,  the  proportion  of  intermediate  lower  air  increases,  and  the  solar  disc  may 
appear  white,+  an  equivalent  portion  of  the  violet  end  of  the  spectrum  being  now 
arrested.  Still  lower  it  wiU  appear  yellow,  orange,  and  red  in  succession,  as  the  lower 
and  more  vaporous  strata  relatively  increase  in  effective  power,  these  colours  being 
far  more  brilliant  than  we  are  accustomed  to  see  at  low  levels,  owing  to  the  smaller 

*  See  Section  Y.,  pp.  388  and  396. 

t  For  the  atratnm  is  sapposed  to  consist  of  particles  similar  to  those  which  caused  the  bine  sun  in 
the  tropics.  The  real  colour  of  the  sun  at  great  altitudes  is  here  assumed  to  be  white,  though,  according 
to  Prof.  Lakolst,  it  approaches  violet. 


ON    THE    CAUSE   OF  THE   UNUSUAL   TWILIGHT   GLOWS.  181 

proportion  of  gross  vapour,  dust,  and  impurities,  and  the  greater  length  of  inter- 
vening air.  The  red  colour  of  the  sun,  when  seen  at  sunset  on  a  clear  day  from 
a  mountain  top,  is  brighter  and  purer  than  when  seen  through  a  dense  mist  at 
midday  to  leeward  of  a  large  town  which  bums  smoky  coal.  The  red  tints 
reflected  from  the  loftiest  Alpine  summits  and  high  clouds  at  sunset  show  more 
brilliancy  than  those  reflected  from  lower  clouds,  partly,  no  doubt,  owing  to  the 
contrast  of  the  increased  darkness  and  the  absence  of  other  colours  in  the  interme- 
diate air. 

Now,  instead  of  occupying  in  imagination  the  position  in  the  middle  of  the  dust- 
stratum  where  these  changes  in  the  sun's  colour  would  become  apparent,  let  the 
observer  watch  the  stratum  from  the  surface  of  the  earth  from  a  few  minutes  after 
sunset.  If  the  stratum  be  supposed  to  contain  a  multitude  of  small  coloiu'less 
particles,  and  to  be  only  moderately  dense,  the  colour-changes  before  observed  in  the 
fiolar  disc  will  be  seen  by  reflection  in  the  vault  of  the  sky,  and  will  only  be  masked 
by  the  blue  effect  of  the  ordinary  sky  particles  where  the  white  surfaces  are  seen 
least  obliquely,  as  overhead.  The  maximum  effects  of  colour  wiU  occur  where  the 
influence  of  perspective,  unimpaired  by  atmospheric  opacity,  is  greatest,  and  the 
light  strongest  in  comparison  with  that  of  the  intermediate  air.  The  whole  sky 
will  be  illmninated  by  diffuse  reflection  of  the  sun's  rays,  if  the  reflecting  particles 
be  opaque,  and  the  order  of  colours  will  be  uniformly  greenish-blue,  green,  white, 
yellow,  and  red  in  succession,  each  colour  appearing  first  in  the  east,  and  passing 
over  to  the  west.  Even  if  the  surfiices  were  tinted,  somewhat  similar  colours 
would  be  observed,  as  may  be  seen  when  a  bright  yellow  or  red  sun,  in  setting, 
tinges  all  objects  with  the  same  hue.  This  effect  is  especially  noticeable  when  the 
air  is  clear  after  a  heavy  shower,  and  when  diffuse  light  from  the  sky  is  intercepted 
by  clouds. 

But,  do  these  contingent  phenomena  correspond  with  what  actually  took  place 
over  England  in  the  glows  of  December,  1883  ?  On  some  few  occasions  the 
resemblance  was  close,  but  usually  the  strong  coloured  illumination  was  confined  to  a 
part  of  the  sky  between  the  horizon,  near  where  the  sun  set,  and  the  zenith ;  and 
frequently  the  sky  towards  north  and  south  remained  of  the  usual  blue  colour.  From 
December  to  the  beginning  of  February  the  arc  of  colour  contracted  in  area,  and 
occasionally  the  luminous  cloud  shaded  off  rapidly  into  deep  blue  at  the  edges. 
The  luminosity  of  November  9  was  sharply  defined,  but  on  that  occasion  the  matter 
concerned  seemed  not  to  be  spread  over  the  sky,  but  separated  into  distinct  cloud- 
like masses.  At  the  end  of  November  and  beginning  of  December,  the  whole  sky 
was  illuminated  with  yellow  and  red,  in  the  manner  that  might  be  expected  on  the 
foregoing  assumption.  The  blue  and  green  did  not,  however,  appear  clearly  in  the 
east  before  reaching  the  west,  probably  owing  partly  to  the  amount  of  bright  and 
mixed  colour  in  the  still  strongly  illuminated  intermediate  air  soon  after  sunset,    lliis 

general  redness,  seen  in  the  first  fortnight  of  the  remarkable  series  of  after-glows  in 

2  B 


182  THE    HON.   ROLLO    RUSSELL 

England,  always  occurred  when,  in  a  favourable  light  the  white  layer  of  matter  was 
noticed  to  be  particularly  dense,  and  never  occurred  when  the  layer  was  previously 
almost  invisible;  though  brilliant  glows  might  then  be  seen  between  the  western 
horizon  and  the  zenith. 

The  hypothesis,  then,  by  which  the  glows  were  assumed  to  have  been  wholly 
due  to  the  action  of  small  ojyarjue  particles  of  mineral  dust  distributed  in  a  stratum 
of  still  smaller  particles,  fails  to  account  for  the  moderate  extent  and  peculiar 
character  of  the  coloured  arc  on  most  occasions.  It  fails  to  account  for  the 
opaline  whiteness  of  the  sheen  soon  after  sunset,  for  the  great  brilliancy  of  the 
orange  and  red  colouring  in  the  late  twilight,  and  for  the  metallic  cast  of  the 
colours. 

But  let  it  be  assumed  that  instead  of  ordinary  opaque  particles  of  matter,  most 
of  the  larger  particles  in  the  stratum  consisted  of  glass-like  laminae  or  very  thin 
fragments  and  spherules,  and  the  peculiar  characteristics  of  the  after-glows  admit  of 
fuller  explanation.  The  small  dust  of  the  glassy  particles  must  be  imagined  to  lie 
in  all  kinds  of  positions  and  at  all  angles,  according  to  their  form  and  centre 
of  gravity.  The  majority  would  presumably  be  horizontally  disposed,  or,  if  curved, 
would  have  their  convex  side  downwards.  Whether  lying  horizontally  or  hanging 
vertically,  the  situation  directly  above  the  observer  would  clearly  be  unfavourable 
for  reflection  vertically  downwards.  Some  time  after  sunset,  the  maximum  bright- 
ness would  take  place  between  the  observer  and  a  point  vertically  above  the  sun, 
by  regular  reflection  from  smooth  horizontal  surfaces,  and  the  part  of  the  sky 
next  in  brightness  to  the  western  arc  would  be  the  east,  where  the  effective 
reflection  would  be  from  nearly  vertical  surfaces  and  from  spherules,  for  water 
particles  in  clouds  near  the  eastern  horizon  are  strongly  luminous  at  sunset,  and 
vitreous  particles  would  reflect  in  a  similar  manner.  The  sky  in  the  north  and 
south  would  be  little  affected  by  direct  reflection  from  such  particles,  and 
might  sometimes  appear  greenish-blue  by  repeated  reflection  and  scattering  of 
light  from  beyond  through  the  red-arresting  stratum,  but  close  to  the  horizon  a 
certain  amount  of  redness,  less  than  ordinary,  might  appear,  owing  to  scattering 
and  sifting  out  of  blue  rays  by  the  lower  strata  and  to  secondary  reflection  by 
ordinary  dust.  A  greater  density  and  preponderance  of  spherules  and  fragments, 
would  cause  the  whole  sky  to  be  bathed  in  red  or  orange,  as  it  is  occasionally  with 
extensive  cirro-stratus.  For,  when  a  thin  high  ordinary  cloud  spread  over  the  sky 
except  in  the  direction  of  the  setting  sun,  is  illuminated  after  sunset,  the 
spherules  of  which  the  cloud  is  composed  will  reflect  the  sun's  rays  in  every 
plane,  so  that  a  red  colour  is  observable  in  all  directions. 

The  failure  of  the  red  glow  to  appear  overhead,  except  when  the  stratmn 
was  at  its  densest,  would  be  due  (l)  to  the  less  favourable  angle  for  reflection, 
(2)  the  less  depth  of  matter  in  the  line  of  sight,  and  (3)  the  greater  intensity  of  the 
blueness  of  the  sky  which  would  neutralise  the  red.     A  Nicol  prism  revealed  to 


ON   THE    CAUSE   OF  THE  UNUSUAL   TWILIGHT   GLOWS.  183 

Mr.  AiTKEN*  the  red  light  overhead  before  it  appeared  in  the  west  after  sunset, 
even  when  quite  invisible  to  the  naked  eye. 

Now,  let  us  examine  the  grounds  on  which  the  assumption  that  the  lofty  stratum 
actually  consisted  of  glaasy  laminae  may  be  based, 

We  have,  above,  stated  the  reasons  which  favour  the  theory  that  the  stratum  had 
its  origin  in  the  projection  of  a  mass  of  fipe  dust  from  the  volcano  in  eruption  in  the  Strait 
of  Sunda,  \fhen  the  remarkable  long-ejiduring  sky-illuminations  were  first  observed. 
All  reports  agree  in  stating  that  the  fine  dust  collected  at  great  distances  from  the 
volcano  consisted  chiefly  of  fragments  of  pumice  blown  into  very  thin  transparent 
plates ;  and  Mr.  STANLEvt  found  that  the  dust  which  fell  on  tha  Arabella  at  1,127 
English  miles  west  of  Java  Head,  on  August  28,  contained  small  irregular  plates  of 
pumice,  a  vast  number  of  which  seemed  to  be  broken  shells  of  pumice  bubbles,  of 
thicknesses  varying  fron^  '001  to  '002  mm.  Many  of  these  small  pieces  wpre  nearly 
square  and  curved,  but  there  are  types  of  all  forms  incidejit  to  fracture.  A  large 
number  of  thin  plates  are  thicker  on  one  edge  than  on  the  others,  having  the  form  pf 
wedges.  Thje  volcanoes  of  Java  produce  these  thin  glassy  plates  of  pumice  through 
enormous  steam  pressure  in  the  interior  and  the  sudden  expansion  of  the  masses 
blown  out  into  the  atmosphere.  J  Professor  Bonney  found  the  *'  glass  foam "  of 
Krakatoa  to  be  more  expanded  by  internal  steam  pressure  than  the  glassy  dust  of 
the  Andes.  The  fragments  of  bubbles  woul(j,  therefore,  be  thinner  and  finer  than  those 
which  fell  65  mjiles  away  after  an  eruptign  of  Cotopaxi,  pf  wl^ich  Mr.  Whymp^r  found 
that  fi:'om  4,000  to  25,000  were  required  to  weigh  a  grain.  Those  T^hich  did  not 
fall  so  soon  would  of  course  be  far  thinner  and  smaller.  Messrs.  Muri^ay  and 
Renard  §  have  found  by  a  microscopical  examination  of  Krakatoa  pumice  that  its 
fracture  has  probably  been  o\^ng  to  a  tex^sion  like  that  observed  in  Rupert's  drops. 
The  particles  have  ragged  edges  which  show  disruption  of  a  vacuolated  or  bubble-like 
structure,  A  rapid  cooling  and  decrepitation  must  take  place  in  the  passage  of  the 
heated  pumice  masses  through  the  air  ;  and  thus  a  vast  quantity  of  extremely  finely- 
divided  matter  be  carried  ii^to  the  higher  atmosphere. 

Crystals  in  granitic  rocks  and  some  lavas  contain  great  numbers  of  excessively 
minute  cavities,  often  filled  with  liquids.  It  has  been  estimated  that  in  some 
instances  the  number  of  these  minute  liquid  caviti^  amounts  to  from  one  thousand 
miUions  to  ten  thousand  millions  in  a  cubic  inch.|| 

Dr.  Flogel's  researches  IT  on  the  dust  which  fell  on  May  21,  1883,  on  board  the 
Elisaheth,  near  Sumatra,  also  showed  that  by  far  the  greater  part  of  the  asji  is  a 

*  *  Proc.  Roy.  Soc.  of  Edinburgh,'  Jnne  2,  1884, 
t  *  Quar.  Jour.  Roy.  Met.  Soc.,'  vol.  x.,  p.  187. 
X  Bonnet,  *Proc.  Roy.  Soc.,'  1884,  p,  124. 
§  *Proc.  Roy.  Soc.  Ed.,'  Feb.  4,  1884. 
II  JuDD,  *  Volcanoes,'  pp.  61-62. 
t  *Met.  Zeitschrift,'  vol.  i.  (1884),  p.  81. 
2  B  2 


184  THE   HON.   ROLLO  RUSSELL 

colourless  glass,  which  seems  to  be  broken  into  all  imaginable  forms.  All  these  glass 
fi^gments  contain  either  innumerable  air  bubbles  or  they  are  full  of  needle-Uke  small 
crystals,  or  they  combine  these  two. 

The  thickest  fragments  of  burst  bubbles  and  the  heavier  particles  fell  at  or 
within  such  distances  as  the  Arabella  was  from  Krakatoa  ;  but  the  lighter  and 
smaller  particles  were  carried  much  further,  and  would  remain  longer  in  the  air  in 
proportion  to  their  minuteness.  Besides  this,  the  proportion  of  glassy  matter,  which 
was  the  lightest  of  the  ejected  products,  was  found  to  increase  continuously  with  the 
distance  from  Krakatoa. 

As  the  pumice  ejected  by  the  Java  volcanoes  'consists  of  an  aggr^ation  of  vast 
numbers  of  minute  glassy  vesicles,  an  unknown  proportion  of  these  vesicles  would  burst 
on  suddenly  reaching  a  much  lower  pressure  at  a  great  height  in  the  atmosphere ; 
many,  however,  might  still  preserve  their  vesicular  form,  owing  both  to  the  tenacity 
of  their  substance  and  to  the  condensation  of  the  steam  within  by  great  exterior  cold. 
The  sudden  cooling  of  the  exterior  crust  of  a  large  pumice  stone  prevents  the 
disturbance  of  the  honeycomb  atructi^re  within,  and  similarly  the  cooling  of  the 
surface  of  a  very  small  particle  may  prevent  the  diminution  of  pressure  from  affecting 
the  minutest  bubbles  in  the  interior.  We  may  therefore  suppose  that  the  small 
amount  of  vapour  or  gas  which  had  existed  within  at  a  very  high  temperature  and 
pressure  was,  by  cooling,  condensed  to  a  very  small  bulk.  Some  of  these  small 
particles  would  accordingly  float  in  the  upper  air  aa  microscopic,  nearly  vacuous, 
perfect  balloons. 

The  extreme  tenuity  of  volcanic  dust  has  been  proved  on  this  as  well  as  on 
other  occasions.  No  watches,  boxes,  or  iQstruments  were  tjght  enough  to  exclude  it 
from  their  interior.*  Thus  we  may  conclude  that  both  in  the  form  of  vesicles  and 
of  fragments  of  vesicles,  an  immense  volyme  of  glassy  pumice  dust  of  microscopic  and 
ultra-microscopic  minuteness  was  pi  ejected  into  the  atmopphere  on  August  26  and  27.  f 

Now,  what  would  be  the  order  of  phenomena  seen  from  the  surface  of  the  earth, 
assuming  the  existence  of  a  stratum  thus  composed  at  a  height  of  from  80,000  to 
120,000  feet  above  the  surface  of  the  earth  ?  The  general  tendency  of  the  matter 
being  to  deprive  the  sun's  rays  of  a  portion  of  their  red,  as  shown  by  observations  at 
Batavia,  Ceylon,  Labuan,  Cape  Coast  Castle,  etc.,  the  colour  of  the  sun  some  tima 
before  setting,  when  shining  through  a  great  length  of  it,  would  a{^)ear  green  or  blue, 
or  else  less  yellow  and  red  than  usual,  according  to  the  density  of  the  matter.  When 
the  stratum  was  less  dense,  as  it  was  after  the  lapse  of  several  months,  the  sun  would 
only  be  rather  less  red  than  usual  at  and  before  sunset.     After  sunset,  the  excess  of 

•  See  the  ElisahetJCs  experience  (Veebbek's  *  Krakatau,'  p.  89).  See  also  Whtmper's  ezperienoe  on 
Chimborazo  during  the  eruption  of  Cotopaxi.     Bonnet,  *  Proc.  Roy,  Soc./  1884. 

t  Mr.  Goodwin,  of  Kingston,  Canada,  found  the  most  characteristic  objects  in  residue  from  snow 
on  January  13,  1884,  to  be  minute  transparent  grannies  scattered  in  thousands  over  the  field  of  the 
microscope. 


ON  THE   CAUSE   OF  THE   UNUSUAL  TWILIGHT   GLOWS.  185 

green  rays  produced  by  the  passage  of  the  solar  light  through  the  stratum  would  first 
be  reflected  from  the  suitably  disposed  particles  east  of  the  observer ;  but  these  would 
be  partially  neutralised  by  transmission  through  the  lower  air,  and  by  the  ordinary 
reflection  of  reddish  rays  from  dust-particles  in  the  middle  air,  where  the  sun  would 
be  much  earlier  setting  than  in  the  stratum.  Then  the  sky  overhead  would  turn 
somewhat  green,  but  the  strong  blue  colour  of  the  still  illuminated  upper  air  below 
the  stratum  would  mask  it.  In  the  west,  the  green  would  in  a  few  minutes 
become  visible,  yeUow  would  follow,  and  orange  or  pink  next,  owing  to  the  greater 
persistence  of  the  rays  of  larger  wave  length ;  but  as  long  as  the  whole  air  below 
the  stratum  was  strongly  illuminated  by  the  ordinary  twLKght,  the  effects  would 
not  be  very  conspicuous.  The  first  colours  would  be  bright  only  in  the  west,  where 
horizontally  floating  pumice  particles  would  reflect  the  sunlight  more  directly  towards 
the  observer.  Then  a  reddish  glow  would  appear  in  the  east,  caused  by  the  reflection 
of  sunlight  from  those  of  the  particles  which  were  nearly  vertical,  from  small  irregular 
fragments,  and  from  spherules.  As  the  sun  sank,  this  redness  would  pass  across  the 
zenith,  where  it  would  be  often  masked  by  the  strong  blue  sky  colour,  and  would  then 
become  conspicuoifQ  towards  the  western  horizon,  reflecting  the  last  rays  of  the  sun 
setting  at  its  level.  The  red  arc  would  sink  slowly  on  the  horizon,  becoming 
deeper  red  owing  to  the  gifting  out  of  the  more  refrangible  rays  by  the  lower  air ; 
but,  when  still  «|,t  some  height  above  the  horizon,  the  green  portion,  now  below 
the  horizon  to  an  observer  on  the  earth's  surface,  but  which  would  not  yet  have 
sunk  out  of  sight  from  a  point  of  view  at  the  level  of  the  stratum,  would  be  sending 
its  rays  eastwards,  and  wo^ld  affect  the  dust  particles  at  that  height  with  a  tinge 
of  green,  or  with  a  mixture  of  rays  producing  a  dingy  colour  compounded  with  the 
blue  of  the  sky,  The  next  colour  to  appear  in  the  east  opposite  the  place  of  sunset 
would  be  yellow,  by  reflection  from  the  reflecting  arc  in  the  west,  but  this,  again, 
would  tend  to  becon^e  reddish  as  seen  from  the  earth,  owing  to  the  great  length  of  air 
through  yp^hich  it  had  passed.  When,  after  crossing  the  zenith,  the  yellow  appeared 
in  the  west,  it  would  be  tolerably  bright,  but  would  be  modified  by  the  fact  that  the 
under  sur&x^e  of  the  stratum  would  be  receiving  different  shades  of  colour  from  the 
differently  coloured  bands  of  the  first  arc  overlapping  one  another,  and  the  tendency 
would  be  towards  orange,  both  from  the  rapidly  growing  redness  of  the  first  arc  as 
the  yeUow  band  sank  out  of  sight  from  the  point  of  view  of  the  high  level,  and  from 
its  own  descent,  and  consequ^nt  interference  of  the  lower  strata.  The  next  colour  in 
the  east  would  be  red  from  reflection  of  the  last  red  band  of  the  finst  arc  ;  and  this, 
too,  would  soon  appear  with  greater  brilliancy  in  tbe  west,  and  would  deepen  in  tint 
as  it  followed  nearly  the  course  of  the  first  arc.  With  a  deep  red  on  the  western 
horizon,  the  second  after-glow  would  end.  The  fainter  and  less  defined  character 
of  the  second  glow  would  be'  owing  to  its  being  a  reflection  from  the  first  arc  of 
glowing  haze,  and  not  of  direct  sunlight. 

Such  might  naturally  be  taken  as  the  succession  of  phenomena  which  would 


186  THE   HON.   ROLLO    RUSSELL 

occur  by  transmission  through  and  reflection  from  a  stratum  composed  of  small 
reflecting  dust,  partially  transparent  and  partially  opaque,  or  else  consisting  of 
a  mixture  of  transparent  spherules  and  fragments,  having  the  qualities  described  ; 
and  such,  on  the  whole,  was  their  normal  course,  though  there  were  differences 
from  day  to  day,  depending  on  the  density  and  other  qualities  of  the  film,  and 
on  the  distribution  of  clouds  and  vapour.  The  yellow  was,  perhaps,  less  conspicuous 
than  might  have  been  expected ;  but  we  must  remember  that  the  red  would  of 
necessity  be  the  strongest  colour  near  the  horizon  in  ordinary  conditions  of  the 
air,  for,  a  white  light  near  the  horizon  becomes  reddish  by  transmission,  and  that 
the  sun,  when  shining  most  on  the  imder  surfaces — that  is,  just  before  sunset 
at  the  high  level — would  be  rod.  Before  sunrise  the  yellow  frequently  covered 
a  large  part  of  the  sky,  and  lasted  many  minutes,  succeeding  the  red  in  the  primary 
and  secondary  glows.  The  succession  of  colours,  which  took  placQ  slowly  at  the 
high  l^vel,  appeared  in  a  corresponding  manner  on  the  lower  clouds  in  November 
and  December.  Small  detached  cumuli  overhead  turned  green,  while  the  sky 
above  them  was  first  blue,  then  pink  or  orange,  showing  that  the  green  light  in 
the  we^t  still  shone  on  their  lower  surfaces,  forming,  as  it  were,  their  secondary  glow, 
while  the  sky  above  was  reflecting  direct  sunlight.  Sometimes  they  remained  pink 
for  an  hour  or  more,  reflecting  the  light  of  the  reflected  red  on  the  horizon,  and 
uns^ffected  by  the  colours  too  high  above  the  horizon  to  shine  on  the  under  surfaces. 
This  persistent  tint  is  evidence  of  the  mere  preponderance  of  certain  transmitted 
parts  of  the  spectrum  in  producing  bright  colorations,  and  of  the  power  of  the  lower 
stratum  of  air  to  change  the  preponderating  transmission  from  green  to  red,  The 
anjount  of  colour,  when  there  was  little  redness  left  on  the  horizon,  even  probably 
at  the  level  of  these  cumuli,  showed  the  effect  of  a  small  quantity  of  light  p^  clouds 
in  a  dark  sky.  If  the  stratum  of  dust  had  been  of  a  density  comparable  to  that 
of  light  cumulus,  and  more  transparent,  the  illumination  of  the  secondary  glow  would 
have  been  much  stronger  than  it  was. 

The  striking  predominance  of  red  in  the  fore-glows  and  after-glows  was  owing, 
first,  to  its  greater  contrast  with  the  blue  sky ;  secondly,  to  the  greater  surrQunding 
darkness  when  it  appeared  ;  thirdly,  to  the  lower  position  of  the  sun  favouring 
reflection  from  the  lower  surfaces  of  the  stratum  to  the  earth  ;  and,  fourthly,  to  the 
red  being  the  last  colour,  and  therefore  less  mixed  with  others.  To  these  may  be 
added  the  better  penetrating  power  of  red  through  the  lower  strata  of  the  atmosphere. 

In  several  descriptions  of  the  after rglows  the  red  coloration  is  described  as 
appearing  in  the  west  and  then  extending  upwards  towards  the  zenith  ;  and  this  was 
frequently  observed  in  England.  In  the  magnificent  after-glow  of  November  9,  in 
Surrey,  the  colour  grew  upwards  both  in  the  primary  and  in  the  secondary  illumina- 
tion. As  a  matter  of  fact,  the  red  light  must  have  been  passing  from  east  to  west, 
but  the  position  of  the  part  of  the  stratum  situated  over  the  western  horizon  would, 
owing  to   perspective   and   the   more  favourable   angle  for  regular   reflection  from 


ON   THE   CAUSE   OF    THE    UNUSUAL   TWILIGHT   GLOWS.  1S7 

most  of  the  particles  at  a  small  altitude  above  the  horizon,  cause  the  faint  beginning 
of  the  glow  from  the  lower  surface  to  appear  to  the  observer  before  a  stronger  reflec- 
tion would  manifest  itself  at  all  nearer  the  zenith.  Frequently  a  certain  amount  of 
redness  appeared  between  10°  and  40°  above  the  horizon  some  minut.es  before  the 
whole  western  sky  was  illuminated ;  but  on  other  occasions  the  red  reflection  moved 
steadily  from  the  zenith  to  the  horizon,  and  before  sunrise  on  the  days  of  maximum 
colour  it  rose  from  near  the  horizon  to  the  zenith  and  passed  westwards,  leaving 
the  east  of  a  light  straw  colour  or  green. 

On  some  occasions  the  southern,  and  on  others  the  northern >  part  of  the  sky  was 
more  strongly  illuminated  than  the  rest  In  many  of  the  observations  in  the  southern 
hemisphere  this  peculiarity  was  noted,  which  would  merely  seem  to  indicate  a  greater 
density  of  reflecting  matter  in  one  direction  or  anothen  When,  after  some  months, 
only  the  finer  particles  remained,  the  arc  of  colour  was  seen  more  regularly  extended 
over  the  place  of  sunset,  while  the  sky,  towards  north  and  south,  remained  blue. 

The  capability  of  vitreous  surfaces  to  reflect  powerfully  the  light  of  the  setting 
sun  is  experimentally  verified  by  the  reflection  from  distant  window-panes  eastward 
of  an  observer,  as  they  glow  with  an  intense  brilliancy  hardly  distinguishable  from 
that  of  the  sun  itselfw  The  character  of  the  appearance  quite  coincides  with  that  of 
the  after-glows,  though  these  were,  of  course,  softer  and  less  dazzling.  The  Crystal 
Palace,  viewed  at  a  distance  of  8  or  10  miles  at  sunset,  resembles  a  great  fire,  and 
small  windows,  at  shorter  distances,  flame  out  with  surprising  intensity.  The  helio- 
graph is  an  example  of  the  use  to  which  vitreous  and  metallic  reflection  has  been  put 
in  conununicating  through  great  distances.  When  it  is  remembered  that  the  after- 
glows took  place  when  the  intervening  air  was  no  longer  in  sunshine,  but  in  deep 
shadow,  their  brilliancy  is  by  no  means  disproportionate*  Panes  of  glass  suspended 
in  mid-air  westwards  would  certainly  display  a  similar  luminosity  from  their  under 
surfaces.  In  like  manner  a  rippling  sea  or  lake  reflects  dazzlingly  the  rays  of  the 
setting  sun,  the  waves  presenting  to  them  a  great  variety  of  inclinations.  That  a  thin 
and  previously  almost  invisible  film  of  transparent  particles  can  reflect  conspicuously 
the  red  light  of  the  setting  sun  is  frequently  proved  by  light  cirrus  streaks  floating 
at  altitudes  between  30,000  and  40,000  feet.  The  much  greater  brilliancy  of  the 
coloration  in  the  west  than  in  the  east  in  the  after-glows  would  be  due  partly  to 
the  position  of  the  fragments,  for,  the  great  majority  would  be  floating  horizontally, 
but  the  same  eflfect  takes  place  with  the  spherules  of  water  in  light  clouds. 

Taking  the  refractive  index  of  pumice  as  about  the  same  as  that  of  glass,  viz., 
1  "50,  the  small  laminae  would  show,  more  or  less  strongly,  the  colours  of  thin  plates, 
if  tolerably  equal  in  thickness,  at  thicknesses  less  than  about  70^00  of  an  inch  ;  but, 
beyond  about  3W000  ^^  ^^  inch,  would  not  reflect  much  light  falling  upon  them,  and 
beyond  2000000  ^f  ^^  ^^^^  would  practically  reflect  none  at  all. 

Probably  the  particles  varied  greatly  in  thickness,  and  would  in  white  light 
reflect  a  variety  of  colours,  so  that  the  general  effect  would  be  colourless  or  white.    If 


IflS  THE    HON.    ROLLO    RUSSELL 

an  effect  of  coloration  had  been  due  to  interference,  a  part  of  the  sky  high  above  the 
horizon  would  not  quickly  have  changed  in  regular  order  from  red  to  yellow  and 
green,  as  it  did,  before  sunrise  and  conversely  after  sunset.  The  colours  of  thin  plates 
may,  however,  have  had  something  to  do  with  the  opalescent  effects  occasionally 
noticed  above  the  setting  sun  and  after  sunset,  and  the  persistent  faint  pink  and 
green  tints  sometimes  succeeding  the  brighter  colours  before  sunrise. 

On  the  theory  of  mere  reflection  of  the  sun's  colour  by  vitreous  surfaces  as  the 
cause  of  the  twilight  phenomena,  we  must  still  assume  the  particles  to  have  been  not 
less  than  about  soq^qoo  of  an  inch  in  thickness,  in  order  to  reflect  much  light,  coloured 
or  white,  and  since  particles  which  fell  on  the  Arabella  at  about  1,140  English  miles 
west  of  ELrakatoa  were  between  ^aooo  ^^d  35^^)0  of  an  inch  in  thickness,  the  proba- 
bility is  that  the  mean  thickness  of  the  much  finer  particles  in  the  glow-causing 
stratum  lay  between  gg^^o  and  ^oo\)oo  ^^ ^"  i^^^^-  Particles  thinner  than  ^ooooo  ^^ 
an  inch  would  not  be  effectual  in  reflection,  except,  perhaps,  from  their  edges,  but  might 
absorb  some  portion  of  the  spectrum.  In  this  way  the  light  reaching  the  reflecting 
particles  may  have  been  altered  by  transmission  through  the  smaller  dust.  As  before 
stated,  the  microscopic  examination  of  pumiceous  matter  reveals  remarkable  facts 
regarding  its  constitution.  High  microscopic  powers  show  in  a  slice  of  lava  cloudy 
patches,  which  can  be  resolved  into  distinct  particles  only  by  still  higher  powers.* 
These  particles  seem  to  consist  of  very  minute  crystals  or  embryo  crystals.  The  majss 
of  matter  ejected  from  a  volcano  like  Krakatoa  and  disseminated  in  the  upper  air 
may  consist  of  similar  vesicles  or  fragments  blown  out  without  the  opportunity  of 
conglomerating  in  the  liquid  state,  and  the  size  of  the  particles  would  correspond 
with  that  required  to  produce  the  atmospheric  effects. 

The  after-glows  of  1883,  when  at  their  maximum,  presented  certain  features 
which  indicated  that  they  might  be  due  not  wholly  to  transparent  reflecting  surfaces, 
but  partly  to  small  dust  of  a  more  ordinary  kind.  Thus  the  visibility  of  the  glow 
over  a  large  part  of  the  sky,  and  its  occasional  appearance  even  at  the  zenith,  might 
be  produced  by  diffuse  reflection,  and  not  by  the  regular  reflection  of  vitreous  particles. 
These  non-transparent  particles  might  be  much  smaller  than  the  regular  reflectors, 
and  still  reflect  any  light  which  fell  upon  them;  t  while  even  smoke  has  some  reflective 
power  in  strong  light.  But  opaque  dust  is  not  necessary,  and  would  hardly  have 
been  adequate  to  produce  all  the  observed  effects ;  and  here,  again,  we  may  note  that 
thin  and  lofty  clouds  reflect  red  light  after  sunset,  from  all  parts  of  the  sky. 

The  question  of  the  floating  power  of  small  particles,  such  as  those  which  pro- 
bably composed  the  haze  in  the  present  case,  is  dealt  with  in  Section  VII.,  p.  441. 

The  capacity  of  the  stratum  largely  to  reflect  light  of  all  colours  is  shown  by 
the  change  of  colour  of  that  part  of  it  which  was  overhead,  from  rose  tint  to  pink, 
orange,  yellow,  and  finally  white,  just  before  sunrise,  and  by  its  occasional  appearance 

•  JuDD,  *  Volcanoes.' 

t  Fabadat,  *  Researches  in  Chemistry  and  Physics,  Bakeriau  Lecture.  1857.' 


ON   THE   CAUSE   OP   THE   UNUSUAL  TWILIGHT   GLOWS.  189 

as  a  white  rippled  haze  in  daylight,  soon  after  sunrise  and  before  sunset,  in  England. 
The  green  coloiu*  never  appeared  overhead  just  before  sunrise,  probably  owing  to 
the  masking  effect  of  the  blue  sky,  which  was  then  strongly  illuminated.  The 
sky  is  at  all  times  much  greener  towards  the  horizon  than  overhead,  where  there  is 
not  a  sufficient  thickness  of  lower  air  to  cut  off  the  more  refrangible  rays. 

A  very  interesting  consideration  is  suggested  by  the  disappearance  of  the  white 
stratum  in  full  daylight  in  most  parts  of  the  sky  in  November  and  December,  though 
cloud-like  in  apparent  density  an  hour  before  sunrise.  It  seems  that  as  long  as  light 
shone  upon  a  veil  of  dust  at  a  great  altitude,  and  not  much  upon  the  air  below  it,  the 
greater  part  of  the  matter  which  makes  our  sky  appear  blue  was  ineffective ;  but 
when  the  sun's  rays  traversed  the  whole  intervening  region,  the  blue-scattering 
particles  became  a  veil  for  the  white  above.  It  is  known  by  observation  on  the 
high  Andes  that,  at  20,000  feet,  the  blue  of  the  sky  tends  to  become  dark  blue 
or  black,  thus  showing  that  a  large  proportion  of  the  colouring  matter  lies  below 
that  altitude.  Thus  we  may  assume  that  nearly  the  whole  of  the  matter  concerned 
in  producing  the  ordinary  blue  sky  was  below  the  stratum,  and  if  this  assimip- 
tion  be  a  true  one,  the  disappearance  of  the  white  stratum  in  full  daylight  is 
explained. 

The  silvery, glare  in  the  western  sky  soon  after  sunset,  with  its  remarkable  lustre, 
would  be  produced  by  regular  reflection  from  glassy  surfaces,  while  the  sun  as  viewed 
from  that  altitude  was  still  several  degrees  above  the  horizon.  Almost  everjrwhere 
the  sky  tints  were  noticed  as  strange,  unearthly,  ghastly,  weird,  or  awful,  and  not 
resembling  the  beautiful  sunset  colours  so  frequently  tinging  the  upper  and  lower 
clouds.  In  accounts  of  the  phenomena  from  places  widely  separated,  and  from 
August  26,  1883,  to  January,  1884,  we  have  remarks  on  the  colours  of  the  sky  as 
resembling  lead,  copper,  brass,  steel,  and  silver.  Common  dust  would  not,  so  far  as 
we  know,  produce  these  metallic  colours.*  During  1885  there  was  not  one  sunset  or 
sunrise  which  exhibited  any  of  the  strange  tints  seen  in  1883  and  1884  in  England, 
and,  as  a  rule,  the  sunsets  even  when  clear  were  almost  colourless.  Taking  all  the 
evidence  into  consideration,  the  twilights  of  1883,  1831,  and  other  years  seem  to 
have  owed  their  specially  brilliant  character  to  the  minute  subdivision  of  pumiceous 
matter  by  the  disruptive  force  of  steam  at  high  pressure,  and  for  this  reason  some 
submarine  volcanoes  may  have  produced  atmospheric  effects  disproportionate  to  their 
size  and  altitude. 

The  colours  of  the  western  sky,  20  minutes  after  an  ordinary  sunset  in  England, 
are  commonly  as  follows  :  dusky  brown  near  the  horizon^  above  that  dull  red, 
reddish  or  orange,  pale  yeUow,  dull  greenish-blue,  blue ;  these  colours  being  either 
duU  and  ill-defined,  or  very  pale  and  clear.  The  colours  are  very  seldom  anything 
but  pale  and  ill-defined  when  there  are  no  clouds,  and  often  there  is  scarcely  a  trace 
of  anything  but  grey  and  blue.     At  the  maximum  of  the  glow  phenomena  the  above 

*  KiESSLiNG  experimentally  produced  similar  met-allic  tints  with  transparent  minute  particles. 

2  C 


190  THE   HON.   ROLLO   RUSSELL 

order  was  nearly  reversed,  the  colours  were  far  more  vivid  and  prolonged,  and  of  an 
unfamiliar  character.  There  is  no  record  of  an  order  of  colours  corresponding  in  com- 
pleteness to  that  of  the  glows  of  1883.*  Von  Bezold's  description  of  normal  twilight 
does  not  at  all  accord  with  what  was  then  observed.  In  these  glows  the  ordinary 
colour  on  the  horizon,  when  visible,  was  perhaps  less  bright  than  usual.  No  dark 
segment  like  that  described  by  Von  Bezold  appeared  in  the  east.  No  feebly 
illuminated  circular  disc,  sinking  fast,  was  observed.  The  after-glow  occurred  when 
the  sun  was  4°  or  5°  below  the  horizon,  and  sank  only  slowly.  No  "  second  dark 
segment ''  appeared  in  the  east,  unless  the  absence  of  colour  other  than  blue,  and 
the  gradually  increasing  darkness,  may  be  described  as  sucL  A  slight  re-illumina- 
tion of  the  east  occurred  when  the  first  after-glow  had  sunk  rather  low,  and  then  this 
ro-illumination  appeared  conspicuously  in  the  western  sky  as  the  secondary  after- 
glow. The  differences  between  the  abnormal  and  the  normal  twilight  may  have 
been  largely  due  to  the  difference  of  altitude  of  the  reflecting  particles  concerned 
in  them. 

It  may  be  desirable  to  compare  the  order  of  reflected  colours  from  common 
clouds  in  an  ordinary  sunset  with  that  observed  during  the  twilight  glows. 

On  January  31,  1886,  the  air  was  clear  in  the  afternoon,  with  a  strong  west 
wind  and  a  blue  sky,  flecked  with  a  few  small  masses  of  cumulus.  The  general 
state  of  the  air  at  sunset  was  not  unlike  that  of  November  9,  1883,  except 
that  there  were  only  a  very  few  clouds  on  that  occasion.  But  on  January  31, 
1886,  the  condition  of  the  upper  air  was  normal,  and  therefore  served  well  for  com- 
parison with  the  strange  developments  of  colour  on  November  9, 1883.  The  sun  was 
nearly  white  about  25  minutes  before  setting,  then  light  yellow,  yellow,  orange,  and 
red  in  succession,  setting  behind  a  very  low  and  slight  bank  of  clouds.  About  10 
minutes  before  sunset  the  small  cumuli  in  K,  N.,  S.,  and  W.  were  light  yellow  or 
buff  on  their  under  surfaces,  and  gradually  turned  into  a  pinkish-yellow  and  pink  or 
red  in  correspondence  with  the  sun's  colour  as  seen  from  the  earth.  They  lost  their 
colour  just  after  sunset,  showing  their  low  altitude.  A  long,  narrow  cloud  in  the  west 
was  much  brighter  directly  above  the  place  of  sunset  than  towards  north  and  south.  The 
sun  set  at  4.45.  At  about  4.50  the  little  cumulus  masses  in  the  east  began  to  timi 
ashy  green,t  in  correspondence  with  the  brighter  and  clearer  green  of  the  sky  above 
the  place  pf  sunset.  At  about  4.56  the  eastern  sky,  beyond  the  little  clouds  near  the 
horizon,  began  to  show  a  slight,  dull,  pink  flush ;  and  this  grew  up,  and  at  about  5.7 
showed  itself  on  the  western  horizon,  and  then  the  greenish  colour  of  the  ciunuli  east- 
wards was  succeeded  by  a'pale  pink  which  attained  its  maximum  with  the  maximum  red- 
ness on  the  western  horizon,  which  was  never  more  than  a  pale  and  weak  illumination. 

*  See  LiAis's  acconnt  of  a  voyage  to  Rio  Janeiro  in  1858,  *  Comptes  Bendns,'  t.  xlyiii.,  p.  109. 

t  The  "  Ix)ichenfarbe  "  of  observers  in  the  Alps,  where  the  high  snowy  tops  turn  red  soon  after 
sunset,  then  ashy  pale,  and  then  again  red  (see  Db  La  Rive,  '  Bibliotheqne  Universelle,'  xxiii.,  xxiv., 
1889,  and  Necker,  *  Annales  de  Chimie  et  Physiqne,'  1839.) 


ON  THE   CAUSE  OF    THE   UNUSUAL  TWILIGHT   GLOWS.  191 

There  was  a  slight  pinkish  light  still  in  the  west  at  5.30,  and  a  very  faint  pro- 
jection of  pink  rays.  The  deep  blue  sky  overhead,  at  5.20,  shaded  towards  the  west 
into  blue  with  the  slightest  visible  tinge  of  purple.  The  succession  of  colours,  there- 
fore, with  cumulus  is  not  unlike  that  in  the  sky  diu-ing  the  strange  glows,  but 
the  duration  is  very  much  shorter.  In  both  cases  the  phenomena  seem  to  be  due 
mainly  to  reflection  of  the  sun's  changing  colour  in  setting,  and  next,  of  the  light 
reflected  by  the  sky  in  the  west,  when  the  rest  of  the  sky  is  already  darkened. 

In  the  case  of  a  high  stratum  of  gauzy  cirrus  which  occasionally,  though 
rarely,  covers  the  sky,  some  changes  of  colour  occur  similar  to  those  of  1883,  though 
the  duratioQ  of  the  colours  is  much  shorter.  Thus,  on  December  16,  1885,  at  Rich- 
mond, in  Surrey,  the  eastern  sky  was  suflfiised  with  red  40  minutes  before  sunrise,  and 
afterwards  with  yeUow ;  but  the  green  and  the  metallic  tints  were  absent,  and  the 
areas  of  colour  were  far  less  definite. 

Cirro-cumulus  covering  the  sky,  with  the  exception  of  a  clear  space  in  the  west,  at 
sunset,  produces  splendid  effects  when  the  sun  sets  clear  red,  the  sky  appearing  like  a 
sea  of  fire,  but  the  condition  is  of  short  duration. 

A  possible  cause  of  the  pinkish  light  which  is  occasionally  seen  in  the  sky 
after  sunset  in  summer  and  autumn  in  Switzerland,  may  be  the  presence,  at  a 
high  level,  of  Sahara  dust,  which  could  travel  the  distance  in  a  very  short  time,  and 
is  known  to  affect  the  atmosphere  far  out  in  the  Atlantic,  sometimes  even  to  the 
extent  of  being  visible  and  collected  as  dust.  Off  the  west  coast  of  Africa,  near 
the  Cape  Verde  Islands,  when  a  certain  wind  blows  from  the  land,  the  air  is  filled 
with  fine  dust,  which  is  deposited  hundreds  of  miles  out  at  sea,  and  the  sun  then 
sets  deep  red,  or  disappears  in  a  kind  of  bank  at  some  altitude  above  the  horizon. 
At  the  edges  of  the  area  thus  affected,  or  where  the  dust  is  less  thick,  a  red 
coloration  is  sometimes  seen  in  the  sky  long  after  sunset.* 

The  red  twilight  of  Egypt  and  North  Africa,  and  on  the  borders  of  the  desert, 
prevails  especially  in  the  summer  and  autumn,  and  appears  to  be  caused  by  the  rays 
of  the  sun,  which  has  set  red  at  the  earth's  surface,  stiU  illuminating  the  minute  dust 
which  pervades  the  air  up  to  a  considerable  height  at  that  season. 

ARAGOf  explains  as  follows  the  prolonged  twilights  of  1831,  which  accompanied 
the  dry  fog  of  that  year : — "  If  the  fog  reflected  that  light,  it  necessarily  occupied  in 
the  atmosphere,  or  beyond  its  limits,  regions  extremely  elevated,  but  yet  not  so  much 
as  would  be  deduced  from  the  ordinary  calculations  of  twilight ;  which  calculations, 
in  effect,  are  based  on  the  hypothesis  of  a  simple  reflection  ;  whilst  it  can  be  proved 
by  recent  experiments,  of  which  it  is  not  possible  here  to  give  an  exact  idea,  that 

♦See  LiAis,  in  *Comptes  Rcndus'  xlviii.,  p.  109,  respecting  phenomena  in  Atlantic,  July,  1858. 
See  alao  Howard's  *  Climate  of  London,'  vol.  iii.,  pp.  48,  49, 192.  Also  the  log  of  the  Viola,  May  24th, 
27tb,  1883,  quoted  in  Section  II., '  General  List,'  p.  265. 

t  Arago,  *  On  Comets.'     Translated  by  Gold,  1833,  p.  85. 

2  C  2 


192  THE   HON.    ROLLO    RUSSELL 

oompound  or  multiple  reflections  play  the  greatest  part  in  all  the  phenomena  of 
atmospheric  illuminations.  When  it  is  agreed  that  the  fogs  shall  be  considered  high 
enough  to  explain  from  them  the  existence  of  the  strong  nocturnal  lights  which  were 
observed  in  Berlin,  Italy,  &c.,  the  red  colour  of  that  light,  however  intense  it  is 
supposed  and  has  really  been,  causes  no  farther  embarrassment  to  the  naturalist,  and 
I  shall  not  be  delayed  by  it." 

On  December  13,  1856,  during  a  fall  of  ashes  from  Cotopaxi,  30  miles  distant, 
a  purple  sky  was  noted.* 

The  remarkable  skies  of  Peru  and  the  Pacific  westwards,  the  arrebol  of  the 
coast  of  Brazil,  and  other  unwonted  twilight  colours,  are  noticed  in  Section  IV.,  p.  342. 

The  following  observations  made  in  Ceylon  tend  to  confirm  the  supposition  that 
the  after-glow3  owed  their  colour  to  reflection  of  the  sun's  setting  light : — 

"  Neither  we,  nor  any  who  have  yet  recorded  their  observations,  can  remember 
the  zodiacal  light  being  coloured  green.  There  was  the  persistence  of  the  colouring  for 
three  successive  days,  too.t     .     .     . 

"  The  sun  seems  to  have  quite  recovered  his  brightness,  and  all  signs  of  the 
peculiar  green  or  bluish  appearance  he  presented  a  few  days  ago  have  vanished.  For 
the  last  evening  or  two,  however,  a  remarkable  lurid  glow,  as  from  an  immense  con- 
flagration, has  been  noticeable  all  over  the  western  sky  long  after  8unset."J 

Thus,  while  the  sun  remained  blue  or  green  at  setting — that  is,  from  September 
9  to  12 — the  sky  seems  to  have  been  coloured  green  after  sunset,  and  when  the  sun 
resumed  its  red  colour  the  red  after-glow  became  conspicuous. 

'*  On  the  13th  and  14th  [September],  at  about  7  in  the  evening  [about  an  hour 
after  sunset],  the  western  part  of  the  horizon  was  lit  up  by  an  unusual  brilliant 
red  light.  It  lasted  for  about  a  quarter  of  an  hour  or  so,  and  then  gradually 
disappeared.  "§ 

"  Yesterday  morning,  when  the  sun  rose  a  little  above  the  horizon,  it  looked  very 
beautiful,  being  of  a  soft  greenish  tint ;  and  as  it  set,  instead  of  the  golden  streaks  it 
leaves  behind,  we  saw  only  a  sort  of  greenish  light.     It  still  continues  the  same."|| 

Other  observations,  however,  in  both  hemispheres  show  that  on  several  occasions 
the  sun  towards  setting  was  blue  or  green  before  a  brilliant  red  or  orange  twilight 
coloration.  On  September  3,  at  7°  S.,  33**  W.,  the  north  horizon  was  very  red  at 
4  a.m.,  and  at  7  a.m,  the  sun  was  pale  blue.  On  September  3,  at  3°  6'  S.,  27°  4'  W., 
the  haze  was  fiery  red  before  sunrise,  and  the  sun,  when  it  appeared,  was  white.  On 
September  10,  at  Bellary,  for  three-quarters  of  an  hour  before  setting,  the  sun  was 
green  ;  after  sunset,  for  fully  40  minutes,  the  whole  western  sky  was  lighted  up  by  a 

*  *  Nature/  vol.  xxix.  (1884),  p.  612. 

T  'Ceylon  Observer,'  September  U,  1883. 

X  '*  Star-gazer,"  in  letter  dated  Pallai,  St^ptember  14.    *  Ceylon  Obsei-ver,'  September  20,  1883. 

§  *  Times  of  Ceylon/  September  20,  from  Jaffna. 

II  'Times  of  Ceylon/  September  28,  1883. 


ON  THE   CAUSE    OF   THE   UNUSUAL  TWILIGHT   GLOWS.  193 

brilliant  red  glow.  At  Poochin,  on  September  10,  a  pale  green  sun  and  red  sky  are 
reported.  On  September  11,  in  the  Red  Sea,  the  sun  was  green  at  rising  and  setting, 
and  there  were  bright  after-glows,  the  order  of  colours  from  the  horizon  being  yellow, 
orange,  red.  At  Madras  the  sky,  on  September  12,  1883,  was  of  an  intense  reddish- 
yellow  colour  at  5  a.m.,  and  at  5.26  a.m.  the  east  was  deep  red,  and  the  rest  of  the 
sky  greenish-yellow.  The  sun  rose  at  5.50  of  a  bright  yellowish- white  colour.  Thus 
there  can  be  no  question  that  a  white,  green,  or  blue  coloration  of  the  sun  near  the 
horizon  was  not  incompatible  with  an  antecedent  or  a  subsequent  red  coloration  of 
the  sky.  Conversely,  in  England,  the  sun,  immediately  before  sunrise  and  aft.er 
sunset,  as  a  rule,  rose  and  set  red  or  orange,  and  yet  a  part  of  the  sky  was  coloured 
green  or  greenish-yellow. 

But,  as  a  rule,  the  fore-glows  and  after-glows  were  far  brighter  and  redder  where 
the  haze  was  not  very  dense  and  where  the  sun  rose  and  set  of  the  usual  colour. 
Good  observations  in  Ceylon  and  elsewhere  make  it  plain  that  the  sun  in  declining 
changed  from  blue  to  green  and  greenish-yellow,  and  conversely  from  yellow  to  blue 
on  rising,  so  that  we  may  fairly  assume  that  at  a  great  altitude,  where  the  setting  and 
rising  sun  would  be  shining  through  a  much  greater  length  of  lower  air,  the  colour 
last  at  sunset  and  first  at  sunrise  would  sometimes  be  red.  In  fact,  it  is  clear  that 
the  maximum  comparative  influence  of  the  foreign  stratum,  which  tended  to  make 
the  sun  blue,  would  be  exerted,  not  at  sunrise  or  sunset,  but  some  time  after  sunrise 
and  before  sunset,  at  the  lower  surface  of  the  haze  at  the  high  level.  On  very  many 
occasions  the  sun  was  not  seen  on  the  horizon  at  all  from  the  earth's  surface  during  the 
period  of  blue-sun  phenomena,  and  therefore,  as  its  last  visible  colour  was  green,  it 
would  be  described  as  setting  green.  But  where  the  view  was  unobstructed,  and 
when  the  haze  was  not  so  dense  as  to  hide  the  sun  altogether  before  it  reached  the 
horizon,  the  last  colour  in  setting  was  frequently  yellowish -white  or  yeUo  wish-green. 
There  is  no  instance  of  the  sun  setting  or  rising  blue  on  the  ocean  (where  the  view  of 
the  true  horizon  was  unobstructed),  and  being  followed  or  preceded  by  a  red  glow  ; 
but  there  are  several  observations  recording  a  white,  grey,  blue,  or  leaden  sky  before 
sunrise  or  after  sunset,  when  the  sun  appeared  white,  blue,  or  leaden.  Even  if  the 
sun,  as  it  sank  to  near  the  horizon  of  the  high  level,  became  obscured,  as  it  often  did 
on  the  earth's  surface,  by  the  density  of  the  haze,  the  diffused  light  transmitted  might 
be  blue,  green,  yeUow,  and  red  in  succession,  for,  its  declining  rays  would  progressively 
pass  through  a  much  greater  comparative  length  of  lower  blue-arresting  air  than  in 
setting,  as  seen  from  the  surface  ;  and  the  red  would  become  manifest  by  reflection 
from  elevated  particles,  though  the  sun  had  been  seen  to  set  green  on  the  earth's 
surface.  Only  in  the  early  period  after  the  eruption,  and  where  the  haze  was  dense, 
would  the  red-arresting  particles  overcome  the  effect  of  the  ordinary  blue-arresting 
particles  of  the  lower  air  in  a  line  through  the  atmosphere  from  the  high  level  to 
the  setting  sun. 

These   considerations    may   account   for  the    fact    that    red   after-glows   were 


194  THE  HON.  ROLLO  RUSSELL 

undoubtedly  seen  in  a  few  places,  when  the  Bun,  not  long  before  eunset,  had  been 
seen  blue  or  green.  In  one  or  two  cases  the  effect  may  have  been  owing  to  the  sun, 
after  sunset  took  place  on  the  earth,  having  passed  beyond  the  overlying  stratum  and 
having  reached,  from  the  point  of  view  of  the  stratum,  a  clear  space  in  the  far  west 
as  yet  unaffected  by  its  absorptive  or  scattering  influence,  whence  the  sun  would  cast 
its  usual  ruddy  light  on  the  particles  at  a  great  altitude  above  the  western  horizon. 
This  may  have  been  the  condition  producing  the  red  illumination  at  Trinidad  on 
September  2  ;  and  the  fiery  redness  of  the  sky  before  the  sun  rose  dazzlingly  white 
{Qv£en  of  Cambria,  3°  6'  S.,  2T  4'  W.),  on  September  3  may  have  been  owing  to 
the  sun,  before  sunrise,  having  from  that  position  been  beyond  the  eastern  limit  of 
the  great  haze  stratum.  It  will  be  noticed  that  usually  the  sky  was  not  seen  red, 
but  white,  grey,  or  blue  before  a  white  or  blue  rising  sun,  and  after  a  white  or 
blue  setting  sun;  and  the  exceptions  may  have  been  due  to  the  reasons  above 
stated. 

North  and  south  of  the  path  of  the  main  body  of  haze  within  the  tropics,  the 
red  glows  were  conspicuous. 

With  regard  to  the  objection  that  a  very  large  quantity  of  dust  would  be 
required  to  be  spread  over  the  upper  air  to  produce  the  glows  which  covered  simul- 
taneously so  great  an  extent  of  surface,  no  good  ground  can  be  adduced  why  very 
small  particles  illuminated  on  a  dark  background,  and  seen  through  darkened  air, 
should  not  combine  to  produce  a  conspicuous  effect ;  a  continuous  film,  not  thicker 
than  0*000,005  of  an  inch,  would  be  sufficient  to  reflect  a  considerable  proportion  of 
white  light.  One  cubic  kilometre  of  fine  dust  spread  over  the  upper  air  would  pro- 
duce a  continuous  thickness  of  0*002  mm.  =  0000,078  of  an  inch  for  the  whole 
surface  of  the  atmosphere,*  or  0*000,156  of  an  inch  for  one  hemisphere,  which  is 
probably  a  greater  surface  than  was  covered  at  any  time  by  the  glow  phenomena. 
And  a  sheet  of  fine  cloud  spread  like  this  dust  in  a  lofty  stratum  over  the  atmosphere 
would  occupy,  a«  water,  a  very  small  cubical  volume,  but  would  be  capable,  in  a  finely 
divided  state,  of  producing  a  visibly  red  sky  with  the  sun  several  degrees  below  the 
horizon. 

The  tails  of  comets  have  been  calculated  to  be  of  so  great  a  tenuity  that  the 
matter  contained  in  a  tail  of  100,000,000  miles  in  length  and  50,000  miles  in 
diameter,  if  compressed,  would  scarcely  amount  to  a  cart-load  :  the  matter  causing 
the  blue  colour  of  the  sky  may  possibly  occupy  a  still  smaller  volume.t  A  strong 
optical  effect  may  thus  be  produced  over  a  vast  space  by  an  extremely  minute 
quantity  of  matter ;  whUe  the  distance  of  the  stratum  from  us  cannot  be  compared 
with  that  of  comets. 

There  appears  to  be  very  great  probability  that  a  quantity  of  fine  dust  pervading 

♦  Ybrbeek's  *  Krakatau,'  p.  157. 

tTTNDALL,  "Scientific  Use    of  the  Imagination,**  *  Fragments  of    Science/  p.  122.    See  also 
IlEKScnsL's  ^  Astronomj.* 


ON  THE  CAUSE  OF  THE  UNUSUAL  TWILIGHT   GLOWS.  195 

the  upper  regions  of  the  air  would,  according  to  the  experiments  of  Mr.  Aitken, 
condense  upon  itself  the  vapour  with  which  it  came  in  contact,  and  that,  with  this 
augmentation  in  size,  the  particles  would  become  visible,  as  thay  were  in  the  twilight 
phenomena.  In  the  present  case,  however,  spectrum  observations  and  the  nature  of 
the  corona,  as  well  as  other  considerations,  do  not  support  this  view,  as  representing 
what  actually  occurred.  Moreover,  we  have  had  experimental  demonstration  on  a 
grand  scale  of  the  competency  of  dry  dust  to  produce  ^(JuaJly  remarkable  atmospheric 
effects.  In  1783  Europe  was  covered  with  a  dense  dry  haze  for  several  months 
during  the  summer,  and  the  sun  was  shorn  of  its  rays  during  a  long  period  of  dry 
weather.  The  haze  extended  from  the  sea-level  to  an  elevation  higher  than  the  tops 
of  the  Alps.  It  followed  a  great  eruption  in  Iceland.  Any  stratum  of  this  haze — say 
5,000  feet  in  thickness — would  probably  have  produced  twilight  effects  like  those  of 
1883  if  it  could  have  been  raised  to  a  sufficient  height  and  the  lower  air  had  been 
clear.  The  air  was  too  dry  at  that  time  to  permit  the  supposition  that  the  dust 
particles  were  loaded  with  water  vapour.  The  particles  do  not  seem  to  have  been 
large  enough  to  be  visibly  deposited  and  to  be  examined  with  a  microscope.  In 
fact,  they  seem  in  character  to  have  greatly  resepibled  the  particles  of  the  haze 
which  succeeded  the  eruption  of  Krakatog,  in  1883,  when  the  dust  particles  were 
carried  to  a  height  where  the  dryness  of  the  air  would  be  extreme  and  where 
clouds  are  never  formed. 

Although  we  do  not  think  that  diffraction  through  the  haze-stratum  accounted, 
without  the  factor  of  reflection,  for  the  series  of  brilliant  colours  witnessed  in  the 
twilights  of  1883,  it  nevertheless  played  a  very  important  part,  just  as  it  does  in  the 
case  of  ordinary  sunrises  and  sunsets.  According  to  the  law  ejaun^iated  by  Lord 
Raylbigh,*  "  When  light  is  scattered  by  particles  which  are  very  small  compared  with 
any  of  the  wave-lengths,  the  ratio  of  the  amplitudes  of  the  vibrations  of  the 
scattered  and  incident  light  varies  inversely  as  the  square  of  the  wave-length,  and 
the  intensity  of  the  lights  themselvea  as  the  inverse  fourth  power."  Consequently, 
the  blue  rays  are  scattered  laterally,  and  an  increased  proportion  of  red  rays  is 
propagated  in  the  direction  of  incidence.  The  particles  of  the  haze^stratum  were 
large  in  comparison  with  ordinary  atmospheric  blue-scattering  particles,  ayid  scattered 
rays  of  the  other  end  of  the  spectrum.  The  remarkable  phepomejia  of  the  glows 
therefore  resulted  from  the  inter-action  of  these  two  oppositely-working  layers  upon 
transmitted  rays,  with  the  aid  of  a  lofty  reflecting  di^strcloud  not  usually  present. 

Thus  we  may  probably  conclude,  that  the  haze  which  followed  the  eruption 
of  Krak^toa,  and  produced  the  twilight  glows,  w^s  compQse4  mjg^inly  of  very  fine 
dust,  and  that  this  (Ju9t  at  a  great  altitude  reflected  the  light  of  the  setting  or 
rising  sun  after  diffractioiiL  through  the  stratum  and  diffraction  and  absorption  by 
the  lower  atmosphere,  and  secondarily  reflected  again  this  reflected  light. 

*  'Phil.  Mag.,*  vol.  xli.  (1871),  p.  111. 


J 


196  PROFESSOR   KIESSLING 

Tlie  foregoing  remarks  may  therefore  be  summarised  as  follows  : — 

1.  The  fall  of  dust,  chiefly  pumiceous,  at  great  distances  from  Krakatoa  west- 

ward, on  the  days  following  the  first  appearance  of  the  red  twilight. 

2.  The  existence  of  a  white  haze  at  a  great  altitude  during  their  prevalence. 

3.  The  great  effect  produced  by  small  vitreous  surfaces  in  reflecting  sunlight 

when  the  intervening  air  is  darkened. 

4.  The  failure  of  the  spectroscope,  on  the  whole,  to  indicate  an  increased 

strength  in  the  lines  due  to  vapour. 

5.  The  structure  of  the  haze,  more  resembUng  that  of  smoke  than  that  of  the 

highest  clouds. 

6.  The  resemblances  and   contrasts  between  reflection  of  sunset   rays  from 

thin  high  clouds  and  from  the  haze  stratum,  both  in  the  first  and  the 
second  after-glows. 

7.  The  sequence  of  colours  con-esponding  with  what  might  be  expected  to  be 

the  changes  of  colour  due  to  the  sinking  or  rising  sun  at  the  altitude  of 
the  stratum. 

8.  Previous  effects  seen  in  years  of  great  eruptions,  especially  1831,  and  in 

places  affected  by  an  excess  of  dust  in  the  air.     {See  also  Section  V.) 

9.  The  extreme  lightness  of  pumice  dust  and  the  theoretical  floating  power  of 

fine  particles,     {See  also  Section  VII.) 

F.  A.  BoLLO  Russell. 

Professor  Kiessling*s  Theory  of  the  After-glows  * 

Herr  Eiesslino  has  made  a  number  of  laboratory  experiments  largely  based  on 
the  discoveries  of  MM.  Couijer  and  Mascart,  and  of  Mr.  Aitken,  regarding  the 
power  of  dust  to  attach  vapour  to  itself,  and  has  extended  his  researches  to  the  effects 
produced  by  small  particles  on  rays  of  light.  He  states  that  fog  consists  of  watery 
spherules,  the  difference  in  their  sizes  making  it  colourless  by  the  overlapping  of 
numberless  diffraction  rings.  When  only  a  few  cubic  millimetres  of  common  dusty 
air  are  introduced  into  a  vessel  containing  dust-free  saturated  air,  a  silvery  trans- 
parent mist  forms,  and  when  the  sun  or  the  electric  arc  is  looked  at  through  this  mist 
it  appears  surrounded  with  a  bluish  or  greenish  briglit  sheen  with  a  broad  reddish 
ring,  exhibiting  all  shades  from  glowing  purple  to  the  lenderest  pink.  These  diff- 
fraction  colours  appear  with  a  peculiar  metallic  glare.  The  smoke  and  dust  particles 
of  the  atmosphere  would  arrange  themselves,  according  to  their  weight  and  8ize, 
in  layere.  As  the  sun  goes  down,  therefore,  the  particles  above  being  smaller  than 
those  below,  the  ring  appears  larger  over  the  setting  sun  than  under  it.     The  lower 

•  Abstracted  from  'Die  Dammerungserscheinungen  im  Jahre  1883*;  see  also  *The  History  and  \^'oik 
of  the  Waruer  Observatory,  Rochester,  N.Y.,  U.S.,  1883-6.' 


ON-  THE   CAUSE   OF  THE   UNUSUAL  TWILIGHT   GLOWS.  197 

layers  also  absorb  Dearly  all  the  light,  so  that  the  white  spot  appears  only  above  the 
sun.  He  says : — "  All  the  twilight  phenomena  may  be  explained  by  the  action 
of  fine  equal-sized  particles  of  dust."  From  his  experiments  he  finds  that  the 
difltaction  of  the  most  strongly  difiracted  red  rays  does  not  exceed  25°  to  30°  from 
the  direction  of  the  sun's  incident  rays.  The  red  colour,  therefore,  would  appear 
at  about  that  distance,  while  nearer  the  sun  there  could  be  no  colour  effect, 
because  the  rays  would  be  passing  through  layers  of  dust  of  very  different  sizes. 
Within  the  cone  of  light,  that  is,  in  a  line  drawn  to  a  point  within  25°  or  30° 
of  the  sun,  the  rays  meet  with  particles  so  various  as  to  re-combine  the  diflBraction 
colours.  The  result  would  be  a  white  or  grey  sheen.  When  the  sun  has  set 
on  the  earth's  surface  there  will  be  no  colour  effect  so  long  as  the  atmosphere 
is  strongly  illuminated,  on  account  of  the  general  scattering  of  light,  which  prevents 
the  action  of  the  upper  stratum  from  becoming  apparent.  The  maximum  effect 
will  take  place  when  the  sun  has  sunk  so  low  that  a  part  of  the  upper  stratum 
between  the  west  horizon  and  the  zenith  is  receiving  rays  parallel  to  itself; 
and  then,  the  particles  being  of  the  same  size,  the  diffracted  rays  will  pass  downwards 
at  the  same  angle  and  reach  the  eye  of  the  observer  further  east,  already  in  deep 
shadow.  From  this  mist  zone,  which  is,  in  accordance  with  laboratory  experiments, 
so  transparent  as  to  be  usually  invisible,  coloured  diffracted  rays  proceed,  and  produce 
first  an  effect  of  colour  east  of  the  observer,  where  they  illuminate  the  lower 
vaporous  layers,  the  colour  becoming  stronger  with  growing  darkness ;  and,  secondly, 
after  about  15  to  20  minutes,  an  appearance  of  luminous  colour  between  the  zenith 
and  the  west  horizon,  the  diBfraction  rays  now  passing  straight  to  the  observer's  eye. 
The  uncommon  prolongation  of  the  twilight  by  the  second  after-glow  seems  to  depend 
on  a  very  diffuse  and  uniform  mist,  those  strata  exercising  a  considerable  diffiuctive 
power  which  are  at  the  outer  border  of  the  segment  reached  by  direct  sunlight,  so  that 
rosy  di&acted  rays  penetrate  into  the  dark  so-called  earth-shadow,  and  light  up  the 
vaporous  matter  there.  The  second  rosy  after-glow,  therefore,  will  be  seen  when  the 
background,  on  which  the  very  weak  diffuse  light  is  set  off,  is  quite  dark — that  is, 
when  the  greater  part  of  the  atmospheric  arc  lighted  by  the  sun  has  sunk  below  the 
horizon.  The  extent  and  intensity  of  the  first  and  the  second  after-glow  must, 
according  to  experiment,  depend  very  decidedly  on  the  homogeneity  of  the  mist. 
When  a  glass  vessel  is  filled  with  homogeneous  mist — so  that,  for  instance,  an  electric 
light  appears  as  the  centre  of  a  green  sheen  surrounded  with  two  red  and  violet 
rings — and  a  few  cubic  millimetres  of  tobacco  smoke  are  introduced,  the  splendid 
colours  are  at  once  lost  in  a  dirty  yellowish  colour,  with  a  reddish  border.  [The 
suggestion  presents  itself  in  connection  with  the  above  argument  whether  the  rusty 
colour  of  the  moon  in  a  lunar  eclipse  may  not  be  due  to  the  diffraction  of  rays  which 
have  passed  through  the  earth's  atmosphere.]  Prof  Kiessung  then  remarks  on  the 
absence  of  the  defined  earth-shadow,  during  the  displays  of  1883-4,  noticed  also  by 
Dr.  VON  Bezold.     Prof.  Kiessung  concludes  that  only  two  causes,  either  dust  or 

2  i> 


198  PROFESSOR   RICCO 

homogeneous  water  particles  produced  by  the  finest  dust,  could  have  given  rise  to 
the  after-glows.  He  thinks  it  not  at  all  improbable  that  by  the  sifting  action  of 
months,  the  dust  of  Krakatoa  should  have  become  so  homogeneous  as  to  account  for 
all  the  effects.  He  has  seen  the  diffraction  rings  even  in  cement  dust  sifted  through 
fine  muslin. 

Although  Professor  Kiessling's  theory  accounts  for  the  solar  corona,  which 
appeared  more  distinctly  several  months  after  the  eruption  than  at  an  earlier  date,  it 
fails  to  explain  points  of  great  importance  in  the  twilight  phenomena.  The  glows 
were  seen  on  the  day  following  the  eruption  and  continuously  thereafter.  The 
particles  could  not  so  early  have  become  sorted  into  layers  of  equal-sized  dust. 
The  diffraction  ring  was  often  visible  after  sunset  in  England,  but  seemed  to  be  a 
distinct  phenomenon  from  the  brilliant  colorations  which  followed  the  paler  hues 
of  diffraction.*  Prof.  Kiessling  accounts  for  the  secondary  after-glow  by  the 
reflection  of  the  first  glow  ;  so  that  he  assumes  a  capability  of  reflection  in  the 
stratum  of  considerable  effective  strength.  But  if  the  stratum  be  capable  of 
reflecting  so  conspicuously  the  sinking  arc  of  the  primary  after-glow,  will  it  not, 
(I  foi'tiori,  reflect  the  direct  rays  of  the  setting  sun  ?  And  if  a  stratum  existed 
of  density  sufficient,  as  we  have  seen,  to  make  the  sky  appear  overclouded  at 
certain  stages  of  the  twilight,  we  cannot  avoid  the  conclusion  that  this  stratum 
would  be  capable  of  strongly  reflecting  the  red  light  of  the  setting  or  rising  sun, 
the  intervening  air  being  deprived  of  its  masking  glare  by  the  earth-shadow.  Now, 
the  time  at  which  the  afterglows  appeared  corresponded  with  the  period  after 
sunset  at  which  the  diffused  matter,  from  other  considerations  respecting  its  height, 
might  be  expected  to  receive  the  hist  rays  of  the  setting  sun.  And  finely  divided 
solid  or  liquid  matter  has  firequently  been  proved  to  be  capable  of  so  reflecting  the 
sun's  last  rays.  It  therefore  does  not  appear  probable  that  difiraction  was  con- 
cerned in  producing  the  principal  effects  in  the  twilight  phenomena,  though  some 
visible  influence  would  undoubtedly  be  exercised  thereby  in  minute  particles  widely 
diffused,  and  in  course  of  time  becoming  more  homogeneous. 

Professor  Riccd's  Views. 

Professor  Ricc6t  has,  in  one  of  his  valuable  articles  on  the  twilight  phenomena, 
stated  the  reasons  which  to  him  render  difficult  the  acceptance  of  Professor  Kiessling's 
theory  of  the  twilight  glows  as  a  part  of  the  corona  surrounding  the  sun.  He  finds, 
first,  that  the  outer  margin  of  the  diffraction  corona  should  be  on  the  horizon  when 

•  The  diffraction  colours  were  occasionally  visible  when  the  bright  glows  were  but  moderate  in 
extent  and  brilliancy.  These  diffraction  colours  were  seen  as  very  pale  pink  and  greenish-white  arcs 
before  sunrise,  moving  upwards  much  less  rapidly  than  the  bright  colorations  from  which  they  were 
quite  distinct. 

f  "  Riassunto  delle  osservazioni  del  crepuscoli  rossi,**  *  Reale  Accademia  dei  Lincei,'  vol.  ii,  Series 
4a,  Session  of  January  8, 1886. 


ON  THE  CAUSE  OF  THE   UNUSUAL  TWILIGHT  GLOWS.  199 

the  sun  is  26°  below  the  horizon.  But  in  reality  the  distamse  of  the  primary  rosy 
arc,  when  on  the  horizon,  from  the  sun  was  only  9°.  Secondly,  the  rate  of  descent 
towards  the  horizon  after  sunset  was  much  more  rapid  at  first  and  slower  near  the 
horizon  than  would  be  the  case  if  the  arc  were  a  part  of  the  corona,  which  would 
descend  at  a  constant  rate.  Thirdly,  the  change  of  form  and  the  dimensions  of  the 
coloured  arcs  were  much  greater  than  can  be  accounted  for  by  the  coronal  theory ; 
for,  the  greater  obliquity  of  the  diffracting  stratum  could  not  produce  such  a  change, 
as  may  be  experimentally  verified.  The  rosy  arc  exhibited  a  great  variety  of  shapes. 
Fourthly,  if  the  rosy  arc  had  been  part  of  a  diffraction  ring,  its  colour  would  have 
been  produced  by  the  superposition  of  red  and  violet  in  two  neighbomring  orders ; 
and  in  the  spectrum,  beyond  the  maximum  of  red,  there  would  have  been  a  maximum 
of  violet,  but  this  was  not  the  case.  Fifthly,  a  corona  has  frequently  been  distinctly 
seen  by  Professor  Tacchini  and  by  himself,  and  has  been  followed  by  only  weak 
or  ordinary  twilight.  In  a  former  article  Professor  Ricc6  had  remarked  on  the 
diverging  beams  as  showing  that  the  glow  was  caused  by  matter  reflecting  direct 
sunlight. 


PART  IV.,  SECTION  I.  (c).* 

The  Blue,  Green,  and  otherwise  coloured  Appearances  of  the  Sun  and 

Moon  in  1883-84. 

By  Mr.  E.  Douglas  Archibald. 

Simultaneously  with,  and  closely  following  upon,  the  eruptions  of  Krakatoa  on 
August  26th  and  27th,  1883,  we  have,  from  different  parts  of  the  globe,  chiefly  within 
the  tropical  zone,  information  of  the  sun  appearing  blue,  green,  silvery,  yellowish,  and 
coppery ;  and  of  the  moon  occasionally  appearing  green. 

In  Section  III.  (a),  p.  312,  of  this  report,  the  geographical  distribution  in  space 
and  time  of  these  appearances  is  given  in  detail. 

In  the  present  section  we  purpose  to  give  a  general  description  of  the  phenomenon 
as  it  was  seen  in  different  parts,  and  briefly  to  discuss  its  physical  cause  and  pecu- 
liarities. 

Before  alluding  to  the  coloured  appearances  of  the  sun  which  followed  the  major 
eruptions  of  August  26th  and  27th,  1883,  we  must  advert  to  some  which  were  seen 
in  the  neighbourhood  of  the  volcano  during  its  minor  eruptions  in  May  of  the  same 

*  In  this  and  sobsequent  Sections  it  should  be  noticed  that  positions  are  sometimes  given  in  English 
notation,  viz.,  degrees  and  minutes,  and  sometimes  in  degrees  and  decimals — the  usual  symbols  indicate 
which  is  employed.  Moreover,  as  on  some  pages  it  is  impossible  to  place  all  the  references  as  foot  notes, 
it  is  well  here  to  state  that  the  list  of  such  will  be  found  at  the  end  of  each  Section. — Ed. 

2  D  2 


^00  MR.   E.   DOUGLAS    ABCHIBALD 

year.  Thus,  following  on  the  eruptions  of  May  20-23,  we  are  told  *  that  at  Kroe,  in 
Sumatra,  to  the  west  of  Krakatoa,  the  "ashes  were  so  thick  that  the  sun  was 
obscured  by  them,"  but  in  this  case  no  mention  is  made  of  the  sun  being  actually 
coloured.  The  first  of  these  appearances,  which  is  the  one  most  important  in  its 
bearing  on  the  cause  of  those  which  succeeded  the  major  eruptions  of  August,  was 
observed  on  board  the  ship  Elisabeth,  (^)t  When  in  sight  of  Krakatoa,  at  9  a.m.  on 
May  20th,  a  white  column  of  vapour  and  ashes  was  seen  to  elevate  itself  to  a  height 
estimated  at  11,000  metres,  or  nearly  7  miles,  by  measurements  effected  (apparently 
by  the  aid  of  instruments)  on  board 

"  After  this  followed  a  rain  of  a  very  fine  grey-yellowish  dust  which  penetrated 
everything,  and  which  continued  to  fall  until  the  night  between  the  21st  and  22nd  of 
May.  On  the  morning  of  the  21st  the  light  was  that  which  prevails  during  an 
eclipse  of  the  sun  ;  the  sky  presented  the  aspect  of  a  large  dome  of  very  thin  opal 
glass,  to  the  vault  of  which  the  sun  seemed  suspended  as  a  pale  blue  globe.  A  fall 
of  dust  was  still  observed  at  a  distance  of  345  English  miles  from  Krakatoa  "  (the 
ship  was  travelling  to  Singapore).  J 

Again,  on  May  20th,  the  Actcta,  in  the  neighbourhood  of  Krakatoa,  6°  50'  S., 
101°  2'  E.,  reports  "  a  peculiar  light  green  colour  was  observed  in  the  sky  to  E.S.E., 
whUe  from  E.  to  E.N.E.  there  was  a  dark  blue  cloud  which  reached  from  the  horizon 
to  the  zenith.  About  2  p.m.  the  day  was  quite  dark,  and  a  very  fine  dust  began  to 
fall,  which  covered  the  ship,  and  only  ceased  about  9  a.m.  on  the  2l8t.  The  sun 
looked  like  dull  silver.  At  noon  on  the  21st,  in  8°  15'  S.,  102''  28'  E.,  the  sky 
remained  of  a  dusty  hue.  The  sky  did  not  assume  a  natural  appearance  until 
the  23rd.  (*) 

Besides  these  direct  observations  of  a  coloured  sun  in  May,  we  have  the  col- 
lateral observations  on  board  the  Belfast  (0,  from  May  24th  to  July  16th,  in 
11°  38'  S.,  31°  44' W.,  to  8°  52'  N.,  85°  52'  K,  of  "a  prolonged  zodiacal  %ht 
and  other  optical  phenomena."  Then,  on  July  16th  and  l7th,  the  Belfast  (^ 
observes  "  a  blue  moon  after  sunset  through  light  haze." 

The  preceding  observations  have  been  quoted  mainly  to  show  the  relation  ot 
the  few  cases  of  coloured  appearances  of  the  sun  and  moon  after  the  minor  eruptions 
of  Krakatoa  in  May  and  June,  to  these  eruptions,  and  their  analogy  to  the  extensive 
series  of  coloured  suns  in  particular,  which  were  observed  after  the  major  eruptions 
of  August  26th  and  27th. 

Here  again  we  have  a  few  observations  near  the  volcano,  in  which  the 
occurrence  of  a  green  sun  is  mentioned,  viz.,  on  August  27th,  at  Batavia,§  the 
sun  was  observed  to  be  green  after  emerging  from  the  cloud  or  smoke  of  the  eruption ; 

*  Vbrbbbk's  *Krakatau/p.  15. 

t  For  numbered  and  letteied  references  in  this  Section,  see  p.  218. 

X  This  passage  is  a  fi'ee  translation  of  one  in  Yerbeek's  *  Krakatan,'  p.  16. 

§  *  Batavia  Dagblad.'     Vebbeek's  *  Krakatan,*  part  ii.,  Notes. 


ON   THE    COLOURED  APPEARANCES  OF   SUN  AND  MOON.  201 

and  on  the  same  day,  and  for  several  days  after,  it  was  observed  to  be  green  by  the 
Hon.  F.  C.  P.  Verbkeb,  at  Labuan  Island.* 

In  the  adjacent  districts  of  Sumatra  and  Java,  the  sun  was  probably  too  obscured 
during  the  greater  part  of  the  time  to  be  seen  at  all,  and  the  inhabitants  generally 
were  too  much  absorbed  in  contemplating  the  other  more  striking  eflFects  of  the 
eruption  to  notice  the  colour  of  the  sun ;  but  the  sky  was  noticed  from  Serangt  to  be 
the  colour  of  lead,  and  from  Teloek  Betoeng  t  to  be  the  colour  of  copper  in  the 
direction  of  Krakatoa.  Here  we  have  the  first  quotation  of  the  colours  of  two 
metals,  afterwards  employed  in  more  than  one  description  of  the  appearance  of  the 
Sim  from  the  Pacific  Ocean  and  other  parts. 

As  the  geographical  distribution  of  the  coloured  suns  in  the  tropics  is  described 
in  detail  in  Section  III.  (a),  p.  312,  we  shall  not  here  follow  their  appearances  in  regular 
succession,  but  state  generally  that  the  results  of  this  investigation  prove  them  to 
have  proceeded  at  first  coincidently  with,  but  within  narrower  limits  than,  the  other 
optical  phenomena  after  August  27th,  in  their  double  revolution  round  the  globe,  and 
within  a  zone  bounded  finally  by  the  north  and  south  tropics. 

Beyond  these  limits  the  blue  or  green  appearance  does  not  seem  to  have 
been  witnessed,  except  sporadically,  and  in  many  cases  only  temporarily,  and 
sometimes  merely  subjectively  by  contrast  with  some  adjacent  red  colour  of 
the  sky. 

In  the  continuous  series  the  last  clear  account  of  a  green  sun,  from  a  ship  near 
the  equator,  is  that  of  the  OlberSy  in  9°  S.,  Sb""  W.  on  September  28th,  1883 ;  but 
subsequent  to  this  we  have  a  notice  of  a  pea-green  sun  at  Bangalore^  and  again,  of 
a  green  sun  in  Ceylon  on  November  9th,  1883.§ 

Also  Professor  Miohie  Smfth,  of  Madras,  seems,  after  his  attention  was  drawn 
to  it,  to  have  noticed  a  green  moon  on  May  14th,  1884  ;  but  this  is  alluded  to 
as  if  it  were  merely  an  occurrence  which  he  had  hitherto  overlooked,  and  which 
occasionally  appears  in  those  latitudes  in  connection  with  excessive  humidity. 

That  in  the  extra-tropics  the  coloured  sun  was  by  no  means  generally  seen,  even 
temporarily,  may  be  gathered  from  the  following  remarks  ; — 

At  Wooster,  Ohio,  U.S.A.,  Professor  O.  N.  Stoddard  ||  says  : — "  In  no  case  has 
the  sun  during  the  day,  or  at  setting,  appeared  green." 

M.  P.  J.  THiiaoK,§  of  Nice,  says : — "  The  blue  sun  has  not  been  observed  in 
our  high  latitudes ;  but  we  have  seen  the  green  moon." 

Professor  Michie  Smith  T  says  : — "  The  green  sun  was  not  seen  further  north  than 

*  'Nature,'  vol.  xxix.  (1883),  p.  153. 

t  VBfiBBEK*s  *  Krakatau,'  p.  59,  Ac. 

X  'Times  of  Ceylon,'  October  6,  1883. 

§  *  Lee  Illuminations  Cr6pusculaires,'  April,  1884;     Reprint  p.  19, 

II  'Nature,'  vol.  xxix.  (1884),  p.  356. 

t  *  Nature,'  vol.  xxx.  (1884),  p.  347. 


202 


MB.   E.   DOUGLAS  ARCHIBALD 


Ongole,  except  at  Vizagapatam,  Eagamundey,  and  Simla ;  and  the  dates  of  observa- 
tions at  these  stations  are  not  preserved.  It  was  observed  at  Bombay,  but  was  so 
inconspicuous  that  it  escaped  notice  at  the  Observatory." 

In  the  extra-tropics  the  coloured  sun  was  seen,  noticeably  by  the  following : — 


Duration. 

Place.                                   Observer. 

Date. 

Temporary  . . 
At  sunset    . . 
Temporary . . 

F6toulefl,l8^re»      ..         . .     F.  Perrin 
Kalmar,  Sweden  f   •  •          • . '             ? 

Cracow  J Dr.  Karlinski  . . 

Kersal  §  (near  Manchester)   1  E.  J.  Bles 

December  24, 1883. 
January  14,  1884. 
January  24,  1884. 
February  26,  1884. 

The  moon,  likewise,  was  observed  to  be  green  in  the  higher  latitudes  by  the 
following : — 


Duration. 

Place. 

Observer. 

Date. 

At  sunset    . . 
At  sunset    . . 

Temporary . . 
At  sunset    •  • 
3  minutes    . . 
3  minutes    . , 

Madrid  II       . . 
Coniston  |     .. 

—      1 
Worcester  || 
Lesina  X 

Kalmar  jl 

Stockholm  ||             ... 

.! 

F.  Gillman 
Arthur  Severn . . 
James  Macaulay 
J.  LI.  Bozward  . 
Bucchich 

? 

? 

'• 

November  30, 1883. 
December  2, 1883. 
December,  1883. 
December  14,  1883. 
January,  1884. 
January  14,  1884. 
January  17, 1884. 

Though  in  many  of  these  cases,  especially  those  of  the  green  moon,  the  colour 

was   evidently  subjective   in   contrast  with  the  adjacent  rosy-tinted  sky,  or  to  an 

eye  long  accustomed  to  red  light,  it  was  expressly  stated  by  some  persons,  such  as 

J.  Macaulay,  Sydney  Hodges,  Dr.  Tripe,  and  others,  to  be  green  when  no  red 

jis  present.     In  the   case  of  the  sun,  it  was  evidently  due  to    the   presence  of 

le  same  haze  which  produced  the  twilight  glows  and  extensive  colorations  in  the 

opics. 

On  the  occasion  of  Venus  being  seen  green  by  Professor  Stoddabd,!  on 
ecember  28th,  1883,  and  January  13th,  1884,  he  says  that  the  light  of  the  planet 
IS  struggling  through  some  invisible  medium  which  arrested  the  other  colours; 
d  in  other  cases  the  presence  of  the  haze  is  frequently  referred  to. 

*  '  L'Asti*onomie,'  3rd  Annee,  p.  67. 

t  *  Les  Illuminations  Cr^pusculaires,'  P.  J.  Thirion. 

I  « Zeitschr.  fur  Met.,'  vol.  xix.  (1S84),  p.  124. 
§  *  Nature,'  vol.  xxix.  (1884),  p.  427. 

II  *  Nature,'  vol.  xxix.  (1883),  p.  179. 
f  *  Nature,'  vol.  xxix.  (1884),  p.  366. 


ON   THE    COLOURED   APPEARANCES    OF   SUN  AND   MOON.  203 

It  thus  appears  that  while  the  material  in  the  tropical  zone  was  dense  enough  to 
produce  a  blue  or  green  sun  and  moon  continuously  during  the  first  few  weeks  after 
the  eruption,  it  was  only  temporarily  able  to  do  so  in  higher  latitudes,  and  under 
conditions  which  tended  to  produce  subjective  contrast  colours. 

Besides  the  blue  and  green  colours  so  frequently  spoken  of,  we  have  accounts  of 
a  coppery,  a  silvery,  and  even  a  leaden  sun  in  the  tropical  zone,  and  in  those  parts 
which  were  reached  by  the  material  soon  after  the  eruption. 

One  of  the  first  observations  of  a  coppery  sun  was  that  made  by  Professor 
Dixon  at  Tokio,  on  August  30th.  (')  This  is  especially  interesting  in  connection  with 
the  exceptional  transmission  of  a  narrow  stream  of  the  haze  towards  this  region,  vid 
Labuan  Island  and  Fisher  Island,  since  it  leads  us  to  conclude  that  this  stream  must 
have  been  of  some  considerable  density.  Similar  coppery  colours  were  witnessed 
only  close  to  the  Equator,  where  the  main  stream  which  travelled  westwards  was  most 
dense.     For  example,  it  was  seen  besides  only  at 

(1)  Fanning  Island,  Sept.  4. 

(2)  1^  20'  S.,  21°  W.,  on  West  Coast  of  Africa  {Corona),  Aug.  31. 

(3)  Guayaquil,  2°  S.,  80°  W.,  Sept.  1. 

In  the  case  of  one  ship,  the  Frieda  Grampp  (*),  the  sun  was  described  as  for 
days  together  looking  like  a  leaden  plate.  Such  colours,  however,  were  only 
exceptionally  observed,  and  the  sun  was  generally  described  as  being  silvery,  blue,  or 
green. 

In  order  to  see  whether  there  was  any  relation  traceable  between  these  different 
colours  and  their  distribution  with  regard  to  locality  for  the  first  ten  days  succeeding 
the  eruption,  we  have  placed  them  in  three  groups  below  : — 


204 


MR.  E.  DOUGLAS  ARCHIBALD 


The  Sun  was  observed — 


Date. 


Bine. 


Qreea. 


Aug.  27. . !  Kokknlai  (*),  Ceylon. 


,.  28.. 

„  29.. 

„  30.. 

»  31. . 

Sept.    1.  • 

11       2, . 


3.. 


Batavia  (*). 
Labnan 
Bangaey  Island 


jo- 


Kokknlai. 
Kokknlai. 
Kokknlai. 
Kokknlai. 

Kokknlai. 

Cape  Coaat  Castle  (*). 

Ship  lO**  40'  N.,  26**  30'  W. 


Bogoti  (•),  4° 43'  N.  .74*  12'  W, 

Maracaibo,  ll**  N.,  72^  W. 

Kokknlai. 

Paramaribo  (•),  6*  N.,  55^  W. 

TrinidadC),  10°  30'  N.,  61°  20'  W. 

Medellin  (•),  6*  2'  N.,  76°  49'  W. 

Ecnador  (•),  3"  S.,  76""  30'  W. 

Cape  Coast  Castle. 

San  Chmtobal   (•),  7^  30'  N., 

72**  23'  W. 
Campano,  10°  36'  N.,  63°  W. 

Maracaibo. 
Kokknlai. 


Kokknlai. 


Maracaibo  (*). 

ZeaUndia,  5^  N.,  ?  170°  W. 


„       6. .  I  Strong  Island  (silver    bine), 
I      ("),  6°  N.,  163**  6'  E. 


„       6. .  I  Zealandia,  6°  N.,  P  170  W. 


Cartagena  (•),  10*^  22'  N., 

75°  32'  W. 
Panama   O,   8**   59'   N., 

79*  32'  W. 


Panama  (^). 
Medellin,  Columbia. 


Jennie  Walker(%  8°  20'  N., 
155°  28'  W. 


Silvery. 


Ida,  (•)  l°-3  N.,  108°-4  E. 

AlbeH  BeifMLun  (•),  2°-3  S.,  4°-7 

Maranham  («),  2°  30*  S.,  44°  W. 
(pale  snn),  and  2°  S.,  5°  E.  (•). 

Gaayaqnil  (*»). 

Maranham. 

Queen  of   Cambria   (0,   9°  S., 

28^  W. 

Varinas  (Veneenela),  8°-6  N., 
70°  W.  (blnish-green  3  p.m. 
to  5  p.m.). 

Onajaqnil. 

Maranham. 


Colombo  ("). 
Honolnln  (»). 


Onayaqnil. 
Maranham. 

0U>er8  (pale  bine),  ('),  T'2  S., 
33°  W. 


Maranham. 

Snperb,  13°  17'  S.,  149°  W.,  and 

for  three  days  thenceforward 

to  5°  S.,  148^  W. 
Tapitenea,  1°  10'  S.,  174°  50'  E. 


Sttperh, 

Papa   (•),  8°1   N.,   161°-4  W. 
(pale  as  throngh  bine  glass). 
Ms^nham. 


ON   THE    COLOURED  APPEARANCES    OF   SUN   AND   MOON.  205 

Thenceforward  we  hear  little  more  of  a  "  silvery  "  sun,  and  the  colour  appears  to 
have  been  mainly  green.  From  the  above  lists  it  appears  that  the  "  blue  "  sun  was 
chiefly  seen  at  great  distances  from  Java,  especially  if  Kokkulai  be  omitted  as  giving 
positive  evidence  of  its  having  been  seen  in  the  Indian  area,  the  word  nil  for  blue 
and  green  being  the  same  in  Singhalese."*^  The  "green"  sun  was  visible  at  first  only 
in  the  Indian  Ocean,  but  afterwards  more  generally  than  either  of  the  other  colours, 
and  finally  the  "  silvery  "  sun,  when  at  a  high  altitude,  appears  to  have  been  almost 
entirely  confined  to  a  narrow  zone  near  the  Equator,  and  more  especially,  on  its 
southern  side.  If  to  this  we  add  the  cases  in  which  the  sun  appeared  coppery, 
dim,  and  sensibly  obscured,  we  find  that  they  were  all  t  close  to  the  Equator  in 
each  hemisphere. 

In  several  cases  the  sun  was  not  visible  when  near  the  horizon.  Thus  the 
Papa,  (•)  in  0""  I'S.,  IGS""  7'  W.,  reports  that  the  sun  on  September  9th  was  hidden 
in  the  yellowish  veil  up  to  7°  above  the  horizon;  and  in  1°  5'  S.  and  165°  W.,  the 
captain  of  the  same  ship  says  that  the  sun  was  still  veiled  with  a  yellow  stratum. 
In  other  parts,  where  it  was  reported  to  be  green  •  or  blue  at  high  altitudes, 
it  was  several  times  spoken  of  as  being  dim  and  giving  little  light  until  it  had 
reached  an  altitude  of  10°  or  more.  Further  irom  the  Equator,  or  from  the  latitude 
of  Krakatoa,  the  green  colour  seems  to  have  been  visible  only  when  the  sun  was  at  a 
low  altitude. 

Thus,  in  Ceylon,  at  Colombo,  on  September  9th,  the  sun  was  observed  to  be  green 
when  about  10°  above  the  horizon.  (*^)  Also,  on  September  10th,  the  Belfast ,  in 
18°  N.,  86°  E.,  reports  the  sun  as  blue  like  the  moon,  at  4  p.m.,  changing  to  green  at 
sunset.  (^ 

On  September  10th,  at  Madras,  the  sun  was  observed  to  rise  of  a  bright  blue 
colour,  and  the  phenomenon  lasted  from  6  to  10  a. m.  (^^) 

On  the  9th,  from  the  Pelican,  10°  4'  N.,  64°  13'  E.,  the  sun  was  noticed  to  be 
gi-een  in  the  morning,  (^*)  and  also  throughout  Southern  India  and  Ceylon,  chiefly 
in  the  mornings  and  evenings.  {^^) 

Mr.  Ladd,  while  passing  through  the  Red  Sea  early  in  September,  1883,  noticed 
that  the  sun,  after  rising  and  before  setting,  and  the  moon  before  setting,  were 
observed  to  be  green  at  an  altitude  of  20°  to  25°  above  the  horizon ;  and  he  noticed 
a  point  important  in  its  relation  to  the  other  phenomena,  viz.,  that  on  the  first 
occasion  "  the  green  moon  was  covered  with  thin  cirro-stratus,  over  which  the  after- 
glow was  cast."  (*®). 

At  Madras,  on  September  12th,  it  was  noticed  that  the  moon,  when  near  the 
horizon,  became  a  pale  green,  and  bright  stars  near  the  horizon  showed  the  same 
tmt.  (") 

Similar  accounts  are  given  elsewhere. 

•  •  Ceylon  Observer/  September  16,  1883. 
t  With  the  exception  of  the  coppery  son  in  Japan. 
2  E 


206  MR.   E.    DOUGLAS   ARCHIBALD 

Thus,  on  September  4th,  in  the  Pacific,  the  Jennie  Walker  observed  the  sun 
green  at  setting.  (•) 

At  Fanning  Island,  on  the  same  date,  the  sun  was  copper  coloured,  and  on 
September  17th  the  Superb^  in  12°  N.  146°  W.,  reports  the  sun  when  rising  to  have 
been  like  a  green  ball.  The  Scotia  12°  N.  51°  E.,  observes  "the  sun  green  on 
rising  "  on  Sept,  9th. 

At  Buenos  Ayres  the  green  colour  seems  to  have  been  noticed  up  to  20°  or  30° 
above  the  horizon.  (•) 

All  this  leads  us  to  inquire  more  closely  into  the  question  whether  the  particular 
colour  observed  was  not  in  part  a  function  of  the  altitude  of  the  sun  above  the 
horizon. 

The  following  circumstances  appear  to  support  this  notion  : — 

At  San  Christobal,  on  September  2nd,  it  was  seen  to  be  "  silvery  at  3  p.m.  ; 
then  it  became  bright  blue,  and  lastly  sky  blue.    At  5  p.m.  everything  looked  blue."  (•) 

At  Cape  Coast  Castle,  on  the  1st  or  2nd  of  that  month,  the  sun  was  described  as 
being  blue  in  the  morning.  It  seems  that  it,  on  rising,  resembled  the  moon,  and  that 
the  clouds  which  passed  over  it,  from  their  greater  rarity  or  their  density,  gave  it 
different  apparent  shades  of  rose  colour,  pink,  and  so  on.  After  the  passage  of  the 
clouds,  its  appearance  through  the  haze  was  white,  like  the  moon.  In  fact,  an 
Englishman  is  said  to  have  taken  it  for  the  moon.  (*) 

At  Barbadoes  it  was  observed  to  be  "  variously  coloured  during  the  day." 

The  Rev.  W.  R.  Manley,  writing  (^®)  from  Ongole,  says : — 

"  On  September  14th  we  had  the  curious  phenomenon  of  a  greenish  colour  in 
the  light  of  the  sun.  .  .  •  About  4  o'clock  an  indistinct  bluish  tinge  appeared  in 
the  light.  This  gradually  passed  into  a  greenish  colour,  and  this  in  turn  became 
tinged  with  yellow  as  the  sun  approached  the  horizon.  As  the  sun  sank,  bands  ot 
smoky  haze  drifted  across  its  disc.  After  the  sun  was  down,  bright  yellow,  orange, 
and  red  appeared  in  the  west,  a  very  deep  red  remaining  for  more  than  an  hour  after 
sunset.  At  night,  the  moon,  just  past  the  first  quarter,  was  seen  surrounded  by  a 
pale  greenish  halo,  about  30°  in  breadth." 

Another  similar  and  important  observation  (^*)  was  made  in  Ceylon  by  a  Govern- 
ment oflScer  while  travelling  from  Mannslr  to  Trincomalee,  and  is  dated  Puleadierakam, 
September  12th.  "The  sun  for  the  last  three  days  rises  in  a  splendid  green  when 
visible,  i.e.,  about  10°  above  the  horizon.  As  he  advances  he  assumes  a  beautiful 
blue,  and  as  he  comes  further  on  looks  a  brilliant  blue,  resembling  burning  sulphur. 
When  about  45°  it  is  not  possible  to  look  at  him  with  the  naked  eye ;  but  even 
when  at  tlie  zenith  the  light  is  blue,  varying  from  a  pale  blue  to  a  light  blue  later  on, 
eomewhat  similar  to  moonlight,  even  at  midday.  Then,  as  he  declines,  the  sun  assumes 
the  same  changes,  but  vice  versd.  The  moon,  now  visible  in  the  afternoons,  looks  also 
tingad  with  blue  after  sunset,  and  as  she  declines  assumes  a  very  fiery  colour  30° 
from  the  zwith," 


ON  THE  COLOURED  APPEARANCES  OF  SUN  AND  MOON.        207 

We  have  quoted  the  foregoing  observations  in  extenso  since  they  evidently  agree 
in  showing  that  the  colour  changed  according  to  altitude,  being  blue  or  paJe  near  the 
zenith,  and  changing  thence  through  a  more  brilliant  blue  to  green  at  from  10^  to  20° 
above  the  horizon. 

When  the  sun  was  below  the  horizon  the  rays  from  it  were  often  in  turn 
coloured  yellow,  orange,  and  finally  deep  red. 

At  Medellin  we  hear  of  even  a  violet,  as  well  as  a  blue  and  green,  colour  having 
been  witnessed.  Obviously,  then,  here  we  have  a  case  of  differential  selective  absorp- 
tion, the  colours,  from  the  zenith  downwards,  being  arranged  in  spectral  order.  If  we 
imagine  the  haze  which  gave  rise  to  these  peculiarities  of  transmission  to  be  composed 
of  particles  capable  of  stopping  the  rays  at  the  red  end  of  the  spectrum  relatively 
more  than  those  at  the  violet  end,  the  phenomenon  admits  of  a  fairly  simple  explanation. 

Up  to  the  present  few  experiments  appear  to  have  been  made  to  determine  the 
precise  tints  transmitted  by  dust  of  different  kinds  when  exposed  to  solar  light ; 
and  to  ascertain  what  proportion  of  the  result  is  due  to  diffraction  and  what  to 
intrinsic  absorption.  Faraday's  experiments*  on  the  colour  of  gold  and  other  metals 
have  reference  only  to  matter  of  intense  opacity  ;  but  the  matter  which  gave  rise  to 
the  present  phenomena  had  little  opacity,  and  therefore  there  is  little  or  no  analogy 
between  the  colours  transmitted  by  metals  or  oxides  in  a  fine  state  of  divisioii  and 
those  produced  in  the  present  case,  probably  by  some  special  absorptive  property  of 
the  dust. 

As  the  particles  which,  in  the  present  case,  produced  the  transmissive  effects, 
may  have  been  different  from  thosje  which  fell  in  the  neighbourhood  of  the  volcano,  it 
is  impossible  to  infer  what  their  optical  properties  were ;  but  it  is  probable  that  for 
the  most  part  they  were  similar  to  the  highly  vacuolated  vitreous  bubble  plates 
described  by  Messrs.  Murray  and  Renard  as  forming  the  major  part  of  the  ejecta 
from  Krakatoa  and  appearing  as  grey-green  pulverulent  matter. 

Whether  such  matter  possesses  special  absorptive  and  transmissive  properties 
or  not  we  are  imable  to  say,  nor  can  it  be  determined  untU  experiments  have 
been  made  with  specimens  of  it ;  but  if  the  mere  question  of  size  would  tend  to 
determine  selective  transmission,  we  might  suppose  that  at  first,  and  where  the 
stream  was  densest  along  the  Equator,  there  was  a  suflficiency  of  both  the  larger 
red-arresting,  as  well  as  of  the  smaller  blue-arresting  particles,  to  produce  a  general 
absorption,  and  thus  a  silvery  light;  that,  further  off,  where  the  stream  was  less 
dense,  at  first  there  were  enough  of  the  larger  red^arrestipg  particles  to  cause  a 
blue  sun,  when  the  sun  was  still  high  in  the  sky  and  shining  through  only  a  com- 
paratively small  thickness  of  the  stratum.  As  the  sun  sank  towards  the  horizon,  and 
its  rays  became  more  obKque,  they  would  traverse  a  larger  extent  of  the  lower 
atmosphere  containing  more  particles  of  vapour  and  organic  dust,   which  generally 

*  *  Phil  Trans,'  1857,  p.  145.    . 
2  E  2 


208  Mil.  E.   DOUGLAS  ARCUIBALD 

appear  by  preference  to  absorb  or  scatter  the  blue  rays.  When  the  sun  was  midway 
between  the  zenith  and  the  horizon,  the  rays  at  both  ends  of  the  spectrum  being  thus 
cut  off,*  the  colour  would  become  green  ;  and  finally,  aa  the  sun  approached  the 
horizon,  and  the  absorption  of,  and  diffraction  by,  the  lower  atmosphere  became  the 
dominant  factor,  the  colour  would  change,  through  yellow  and  orange,  to  red,  as  was 
generally  observed. 

Even  apart  from  the  influence  of  the  lower  strata  of  the  atmosphere,  the  change 
in  the  thickness  of  the  stratum  itself,  traversed  by  the  more  oblique  rays,  would  help 
to  produce  the  same  change  in  the  colour  of  the  emergent  light. 

For  on  the  same  assumption  that  the  haze  exerted  a  selective  absorption  on  the 
red  end  of  the  spectrum,  and  transmitted  the  violet  end  more  freely,  we  should  have 
with  increased  thickness  of  the  stratum  traversed  by  the  rays,  a  tendency  to  a  change 
in  the  colour  of  the  emergent  rays. 

If  i  li  denote  the  intensities,  and  a  a  the  co-efficients  of  transmission  of  the  two 
dominant  rays  transmitted  through  different  thicknesses.  We  have  for  the  thickness  d 
where  the  change  of  colour  would  occur, 

la'  =  t  a' and.'.  0=  ^- ^ ,    ^  , 

log  a  —  log  a 

In  the  present  case,  if  we  assume  the  sun  to  be  blue  at  the  zenith  and  green  at 
an  altitude  of  30^,  we  have 

2=  %  ^80  -  log  168 
log  a  —  log  a 
And  approximately  a  :^  a  ^/S. 

It  is  not  therefore  unreasonable  to  suppose  that  the  effect  of  the  increased 
absorption  of  the  blue  rays  by  the  lower  atmosphere,  with  increased  obliquity  of  the 
solar  rays,  was  partly  assisted  by  the  corresponding  change  in  the  thickness  of  the 
haze  stratum  traversed. 

This  would  accord  with  the  fact  that  where  the  haze  was  most  dense  near  the 
Equator  or  the  latitude  of  Krakatoa,  and  produced  a  pale  or  silvery  tint  when  the  sun 
was  high  (owing  to  its  being  composed  of  particles  of  all  sizes,  and  therefore  transmit- 
ting light  of  all  colours),  the  sun  was  frequently  mentioned  as  being  quite  obscured 
when  within  a  few  degrees  of  the  horizon,  although  otherwise  the  air  was  quite  clear.J 

*  That  the  actual  absorption  was  of  this  character  can  be  gathered  from  the  paper  read  by  Professor 
MiCHiK  Smith  before  the  Royal  Society  of  Edinburgh,  July  7,  1884,  in  which  he  says: — "  When  the  sun 
was  near  the  horizon,  besides  the  absorption  at  the  red  end,  there  was  also  absorption  at  the  violet  end, 
the  spectrum  ending  just  beyond  the  Jine  G." 

t  Here  *'  =  480  for  green  light,  a  coefficient  for  green  light, 
i  =  168  for  blue  light,     a  coefficient  for  blue  light, 
and  the  value  of  ^  at  the  zenith  taken  as  the  unit  of  thickness.     At  an  angle  of  30°  the  thickness 
traversed  will  be  approximately  doubled  .*.  ^  is  put  =  2. 

X   Vide  supra,  and  various  remarks  in  Section  I.  (d),  on  sky  haze. 


ON  THE  COLOURED  APPEARANCES  OP  SUN  AND  MOON.        209 

Subsequently,  we  must  suppose  that  as  the  stream  of  material  became  more 
attenuated  by  spreading  into  higher  latitudes,  three  factors  would  come  into 
play  ;— 

(1)  The  horizontal  extension  of  the  haze  stratum  which  would  tend  to  render 

the  selective  absorption  or  obstruction  ultimately  insensible. 

(2)  The  sifting  out   by  gravitation  of  the    grosser,  and  therefore  presumably 

red-arresting,  particles. 

(3)  The  elimination  of  accompanying  water  vapour,  if  any,  by  evaporation. 

The  combined  action  of  these  factors  and  the  changes  due  to  varying  solar  altitude 
appear  to  afford  a  reasonable  explanation  of  the  diurnal  and  secular  variations  observed. 

The  ultimate  attenuation  of  the  stratum  would  partly  account  for  the  fact  that 
the  sun  was  only  rarely  seen  coloured  at  all  in  high  latitudes,  and  then  only  near  the 
horizon,  being  also  assisted  in  this  respect  by  the  time  taken  by  the  material  to 
spread  into  higher  latitudes,  and  the  sifting  out  which  must  then  have  taken  place 
of  a  considerable  proportion  of  the  larger  red-arresting  particles. 

We  have  omitted  to  consider  the  possible  effects  of  water,  either  in  the  state  of 
vapour,  water-dust,  or  ice-dust,  ejected  along  with  the  pumice-dust,  because  : — 

(1)  There  is  no  reason  to  suppose  that  it  would  act  selectively  on  light  in  a 

different  manner  from  aqueous  vapour  in  ordinary  circumstance,  which 
generally  stops  the  blue,  and  transmits  the  red  end  of  the  spectrum. 

(2)  Evan  if  it  acted  like  the  ice  in  a  glacier,  we  should  have,  by  analogy,  to 

admit  the  presence  of  much  more  vapoiu:  than  could  possibly  exist  at 
such  an  altitude. 

On  the  whole,  it  appetars  most  probable  that  the  dust  stratum,  when  the  sun 
was  shining  through  it  nearly  vertically,  affected  the  light  by  selective  absorption 
chiefly  of  the  raj^s  of  longer  wave  length,  that  as  the  sun  descended,  the  light 
changed  in  colour,  partly  through  a  change  in  the  thickness  of  the  stratum,  and 
partly  by  the  absorption  and  diffraction  through  the  lower  atmosphere,  which 
would  tend  to  act  in  a  contrary  manner,  and  eliminate  the  rays  of  shorter  wave 
length.  Finaljy,  diflraction  through  the  strcttum  and  the  lower  dust,  and  absorption 
by  the  aqueous  vapour  in  the  lower  atniosphere,  would  completely  overpower  the 
selective  absorption  of  the  stratum,  and  allow  a  free  parage  only  to  the  longer  red 
waves. 

Mr.  LocKYEB,  RRS.j  ('')  writing  on  this  phenomenon  when  it  was  first  an- 
nounced, says : — "  The  ejecta  from  the  volcano,  however  high  they  were  cast  into  the 
upper  air,  would  in  the  first  instances  have  had  so  much  coarse-grainednass  about  them 
that  the  light- selecting  qualities  of  the  finest  among  them  would  have  been  entirely 
over-ridden  by  the  coarser  ones,  which  would  be  competent  to  stop  light  of  every 


210  MR.   E.   DOUGLAS   ARCHIBALD 

kind  ....  Let  this  pall  become  thin.  The  sunlight  will  traverse  it  in  part ; 
there  will  still  be  general  absorption,  the  sun  will  be  seen  white,  but  dim.  Now  let 
the  coarser  particles  fall  from  the  upper  air,  leaving  behind  only  those  finer  ones,  the 
blue  and  red  molecules  to  which  I  have  previously  referred.  Neutral  tint  will  now 
give  way  to  green." 

*'  Let  us  assume  first  that  the  quantity  of  red  molecules  was  sufficient  to  over- 
ride the  blue  ones.  At  sunrise  the  blue  molecules  from  the  volcano  would  be  assisted 
in  their  absorption  by  the  blue  molecules  of  aqueous  vapour  always  present.  The  sun 
would  be  green  when  it  first  became  visible.  But  let  the  sun  get  high  ;  the  absorption 
of  the  aqueous  vapour  being  then  reduced  in  consequence  of  the  smaller  thickness  of 
the  air  as  the  sun  rose,  would  allow  the  predominance  of  the  red  absorption  again  to 
assert  itself,  and  the  sun  would  be  blue  at  noon,  though  it  rose  green."  The  red- 
arresting  molecules,  being  coarser  than  the  blue,  would  "  be  the  first  to  fall  from  the 
upper  air  as  dust,  so  tho^t  long  after  they  have  sufficiently  disappeared  to  make  the 
appearance  of  a  blue  or  green  sun  impossible,  there  would  be  enough  floating  material 
in  the  air  at  as  high  a  point  as  the  convection  currents  could  have  carried  it,  to  reflect 
the  sun's  light  after  sunset,  and  to  prolong  the  twilight  in  the  direct  ratio  of  its 
height  above  the  earth's  surface." 

To  give  a  more  detailed  account  than  we  have  hitherto  presented  of  the 
appearance  of  the  green  sun  in  the  tropics,  we  have  thought  it  advisable  to  append 
hereto  the  following  abstract  of  a  paper  read  before  the  Royal  Society  of  Edinburgh, 
on  July  7th,  1884,  by  Professor  Michie  Smith,  of  Madras.  (-') 

The  raritj  of  the  phenomenon  of  a  green  or  blue  sun  makes  it  desirable  to  record  with  the  greatest 
accnracj  and  detail  the  observations  made  during  its  appearance  in  India  in  the  course  of  BeTeral 
dajs  of  September,  1883. 

The  notes  taken  at  Madras  at  the  time  of  the  appearance  will  best  illustrate  the  general  features  of 
the  phenomena : — 

On  September  9,  the  sun,  before  setting,  assumed  a  peculiar  silvery  appearance,  and  its  brightness 
was  so  much  decreased  that  for  about  half  an  hour  before  sunset  it  could  be  observed  with  the  naked  eje. 
This  was  noticed,  I  believe,  though  to  a  less  extent,  on  the  two  days  preceding,  but  I  did  not  myself  ste 
it  on  those  days. 

On  September  10,  frpm  5  to  5^30  p.m.,  the  sun  could  easily  be  looked  at  with  the  naked  eye,  yet  the 
limbs  were  sharply  defined.  At  6.30  the  sun  entered  a  low  bank  of  clouds,  and  did  not  fully  appear 
again ;  but  a  narrow  strip  seen  through  a  rift  in  the  cloud  at  5.43  was  coloured  a  bright  pea-green.  Round 
Madras  this  colour  had  been  seen  in  the  morning,  but  in  Madras  itself  clouds  concealed  the  sun  till  it  had 
risen  to  a  considerable  altitude. 

Of  the  morning  of  the  11th  I  hare  no  record,  but  in  the  evening  the  greei}.  colour  was  brilliant,  ai^d 
was  visible  for  more  than  half  an  hour,  being  preceded,  as  on  the  former  night,  by  the  silvery-whitp 
appearance  of  the  sun's  disk.  Qn  this  evening  a  large  sunspot,  about  y  long,  yrm  so  conspicuous  au  object 
that  it  attracted  the  attention  of  even  the  most  casua)  observers. 

September  12. — At  10.35  a.m.  the  moon,  'which  was  near  the  horizon,  appeared  a  pale  green.  Bright 
stars  near  the  horizon  showed  the  same  tint.  From  5.15  to  5.30  the  clouds  to  the  east  were  coloured 
reddish-brown.  At  5.55  the  sun  rose  with  a  yellowish-green  colour,  but  was  almost  instantly  lost  in 
clouds.     It  reappeared  at  6.4^  and  i^as  then  of  a  bright  green  colour;  this  colour  i*apidly  got  fainter,  bat 


ON   THE   COLOURED  APPEARANCES   OF   SCFN  AND  MOON.  211 

was  qaite  perceptible  till  7  o'clock.  In  tbe  afternoon  the  phenomena  of  the  previons  nights  were  repeated 
and,  the  horizon  being  free  from  clouds,  the  actual  sunset  was  observed.  The  entry  in  my  notes  is : 
'^  6.3. — ^The  sun  set  as  a  greenish-yellow  ball ;  cumulus,  stratus,  and  nimbus  clouds  near  the  horizon,  but 
moon  fairly  clear ;  some  blue  sky,  but  hazy."  The  change  from  green  to  greenish-yellow  was  evidently 
due  to  the  great  increase  in  the  strength  of  the  low-sun-band  close  to  the  horizon,  which  left  the  strip  of 
yellow  between  that  band  and  the  rain-band  by  far  the  most  prominent  feature  in  the  spectrum. 

September  13. — In  the  early  morning  there  was  a  good  deal  of  distant  lightning.  The  sun  rose  of  a 
bright,  golden-yellow  colour ;  no  green  was  seen.     In  the  afternoon  there  were  slight  showers. 

September  14. — Before  sunrise  the  clouds  were  blue  and  grey,  with  patches  of  red  clouds  of  all 
sorts — cirrus,  nimbus,  stratus,  cumulus,  and  mares'  tails.  Two  bright  flashes  of  lightning  about 
5.30  a.m.  In  the  evening  there  was  a  slight  green  tinge,  and  after  sunset  the  sky  was  golden-red  till 
6.50,  while  Mercury,  seen  through  the  red  haze,  was  twinkling  strongly. 

September  15. — The  sun  rose  golden.  In  the  evening  the  sunset  was  very  fine  :  in  the  west  the 
colour  was  golden  to  orange-yellow,  in  the  east  in  was  greenish ;  red  clouds  remained  till  7.5.  There 
were  very  brilliant  red  "  rayons  de  crepuscule,*' 

From  September  15  to  September  20  the  sunrises  and  sunsets  were  very  fine,  with  red  and  gold, 
for  more  than  half  an  hour  before  sunrise  and  after  sunset. 
September  21. — Sunset  normal. 

September  22. — The  sun  rose  as  a  yellow  ball,  and  showed  distinct  greenish -yellow  afterwards. 
From  ten  minutes  before  till  sunset  the  sun  was  greenish-yellow,  but  the  sun  was  much  brighter  than 
on  the  10th  and  11th. 

September  23. — The  sun  rose  very  green.  At  5.37  p.m.  the  sun  appeared  from  under  clouds,  very 
green ;  strong  absorption  in  the  red  end  of  the  spectrum  to  C ;  low-sun-bands  weak.  6.45. — Clouds 
greyish-purple.  There  was  only  one  bank  of  clouds  which  was  near  the  horizon ;  above  this  was  a 
peculiar  greyish  haze.  At  6  the  clouds  were  of  a  marked  purple  colour ;  breaks  near  the  horizon  were 
reddish-  brown.     During  the  night  there  was  a  great  deal  of  sheet-lightning  in  the  south. 

September  24. — The  sun  rose  bright  yellow.  The  spectrum  showed  complete  absorption  up  to  B  ; 
the  rain-bands  a  and  ^  were  very  thick,  and  the  low-sun-bands  less  marked  than  usual.  There  was 
lightning  all  night,  beginning  in  the  south  and  working  round  to  the  south-east.  It  consisted  chiefly 
of  sheet-lightning,  with  occasional  zig-zag  flashes,  but  no  thunder ;  the  stars  were  fairly  clear  except 
near  the  horizon.     Saturn  and  the  moon,  when  near  the  horizon,  were  both  very  dim. 

September  25. — Sunrise  golden-green.  In  the  afternoon  the  shadows  cast  on  white  paper  were  still 
quite  pink,  but  the  sunset  was  bright  yellow. 

September  26. — Much  the  same  as  yesterday. 

September  27. — Before  suni-ise  C,  p,  a,  the  rain-band  and  the  dry-air-band  were  very  strong,  but 
the  dry-air-band  was  less  than  half  as  dark  as  the  rain- band.  The  sun  rose  golden-red.  The  spectrum 
showed  signs  of  clearing  up;  glimpses  of  A  could  be  obtained.  After  dark  there  was  very  bright 
lightning  in  the  west. 

September  28. — Spectrum  still  showed  great  absorption.     Lightning  at  night. 

September  29. — Spectrum  absorption  still  very  strong.  After  dark  there  was  a  display  of  luminous 
clouds  specially  towards  the  east.  After  11  p.m.  there  was  very  heavy  rain,  with  much  lightning  and 
some  thunder.  , 

September  30. — Sunrise  golden.     The  spectrum  on  the  sun  showed  A  clearly,  a  was  very  thick. 
October  2. — In  the  morning,  from  about  7  to  9,  there  was  a  thnnderstorm,  in  which  the  thunder 
was  almost  continuous  for  about  an  hour  and  a  half,  but  although  the  storm  was   almost  vertical, 
hardly  any  lightning  was  visible.  .  .  .  The  total  rainfall  for  the  day  was  4*88  inches. 

Accounts  were  collected  from  trustworthy  observers  in  various  parts  of  India.  All  describe  the 
brilliant  sunsets  of  the  first  week  of  September,  and  record  the  appearance  of  a  green  sun  on  several 
days.     It  was  seen  at  Muttum  in  the  south  of  Madras  on  the  9th,  and  continued  for  several  days  both  in 


212  MR.   E.   DOUGLAS  ARCHIBALD 

the  momiog  and  in  ib«  evening.  The  green  coloar  was  then  lost,  bnt  reappeared  from  the  22nd  to  the 
28th  inclnsive. 

At  Bellary  the  sun  was  seen  "  emorald-g^en  '*  at  rising  and  setting  from  the  10th  to  the  14th 
inclusive.     The  observations  were  not  carried  on  longer. 

At  Coonoor,  on  the  Nilgiris,  the  abundance  of  green  tints  in  the  sunsets  was  noted,  but  the  son 
itself  was  described  merely  as  of  a  '*  shimmerj  *'  appearance. 

The  Spectrum. — The  spectrum  of  the  sun  when  green  was  repeatedly  observed  and  photographed 
with  the  large  zodiacal-light  sp (metroscope,  which  is  furnished  with  one  large  prism  of  dense  ^ass  and  a 
very  long  collimator  permitting  the  use  of  a  wide  slit.  The  main  features  of  the  spectrum  taken  on  the 
sun  when  green  were — 

1.  A  very  strong  general  absorption  in  the  red  end. 

2.  A  great  development  of  the  rain-band  and  of  all  other  lines  that  are  ascribed  to  the  presence 
of  water- vapour  in  the  atmosphere,  more  especially  of  the  group  C^  of  a  and  of  the  band  at  W.L.  504. 

The  absorption  in  the  red  end  was  of  very  varying  intensity,  but  when  the  phenomenon  was  at  its 
maximum  phase  it  gradually  crept  up  from  about  B  till  past  C,  as  the  sun  sank  towards  the  horiaon. 
On  the  12th,  when  the  sun  was  within  a  few  degrees  of  the  horizon,  the  absorption  was  well  marked 
up  to  W.L.  621,  t.e.y  to  beyond  a,  while  at  the  violet  end  the  visible  spectrum  ended  at  W.L.  428,  or  just 
beyond  G. 

The  lines  A  and  a  were  never  visible  even  on  the  sun  when  it  was  green,  and  even  B  oould  be  made 
out  with  difficulty  from  half  an  hour  before  sunset  onwards,  and  before  it  vanished  it  grew  intensely 
prominent,  with  enormously  thick  bands  on  the  less  refrangible  side.  The  band  Cj  on  the  more 
refrangible  side  of  C  became  very  broad  and  black,  while  the  fine  line  between  this  and  C  remained  thin 
and  sharp,  and  C  itself  thickened  out  on  the  less  refrangible  side.  The  rain-band  was  stronger  than  I 
have  ever  before  observed  it  on  the  plains,  and  even  with  the  dispersion  produced  by  a  single  prism  at 
least  eight  lines  could  be  measured  in  it,  while  many  more  were  visible.  The  low-sun-band  was  not 
very  conspicuous,  bnt  this  was  partly  due  to  contrast  with  the  very  strong  rain-band.  The  line  W.L.  568 
at  the  more  refrangible  side  of  the  low-sun-band  was  very  well  marked,  and  the  band  itself  seemed  to 
consist  of  a  series  of  equidistant  lines. 

The  apparently  much  stronger  absorption  in  the  red  than  in  the  blue  end  was  a  very  marked 
feature,  which  became  still  more  conspicuous  when  a  photograph  of  the  blue  end  was  examined. 

Since  the  passing  away  of  the  abnormal  conditions  I  have  made  careful  observations  of  the  sunset 
spectrum  with  the  same  apparatus,  and  I  find  that  ordinarily  A  and  a  are  clearly  visible  as  well  as  B, 
though  at  times  they  are  strongly  marked,  and  a  good  deal  of  shading  is  observable  between  them ;  C^  is 
much  thinner,  and  the  rain-band  is  less  prominent  than  the  low-sun-band,  which,  however,  does  not  now 
have  the  appearance  of  a  number  of  fine  Hues.  The  nearest  approach  to  the  green-sun  spectrum  was 
observed  recently  during  a  severe  thunderstorm,  which  was  accompanied  by  a  fall  of  about  1^  inch  of 
rain.  A  very  similar,  though  less  intense,  spectrum  can  be  observed  almost  any  evening  by  taking 
advantage  of  the  passage  of  a  small  thin  cloud  over  the  sun's  disc.  If  a  lens  be  used  in  front  of  the 
slit  of  the  spectroscope,  the  absor|7tion  due  io  the  cloud  will  be  seen  as  a  band  in  the  middle  of  the 
bright  spectrum  from  the  unclouded  part  of  the  sun,  and  owing  to  the  strong  contrast,  the  details  of  the 
absorption  will  be  well  seen,  just  as  in  the  case  of  the  spectrum  of  a  sunspofc. 

Meteorological  Phenomena. — The  electrification  of  the  air  was  carefully  studied  during  the  green 
sun  period,  and  the  results  are  rather  curious.  From  September  3rd  to  Gth  the  potential  of  the  air  was 
positive  in  the  early  morning,  diminished  to  zero  between  9  and  10  a.m.,  then  became  negative,  and 
remained  so  until  the  sea-breeze  came  on  in  the  afternoon,  when  the  charge  was  positive  i^z^n.  and 
continued  so  all  night.  The  amount  of  electrification  varied  greatly  and  rapidly.  On  the  7th  and  9th 
the  potential  was  positive  all  day,  on  the  8th  it  was  negative  for  a  short  time.  From  the  10th  to  the 
12th  it  varied  in  the  same  way  as  from  the  3rd  to  the  Gth,  and  this  state  of  matters  was  repeated  from 
the  20th  to  the  27th  ;  the  electrometer  readings  from  the  13th  to  the  19th  having  been  noi*ma1.     All  the 


ON  THE  COLOURED  APPEAKANCBS  OF  SUN  AND  MOON.        213 

negative  readings  were  got  daring  a  hot  land  wind  from  the  west.  Between  the  6th  and  9th  of 
September  a  storm  of  unnsoal  violence  swept  over  the  Madras  Presidency  from  the  sonth-west  to  the 
north-east,  making  itself  felt  in  different  ways  at  different  places.  The  rainfall  for  September  was 
nnusaallj  small  all  over  Madras.  The  average  for  fifteen  stations  was  3*24  inches,  not  qnite  half  the 
average  for  this  month  during  previous  years. 

The  barometric  curves  for  Colombo,  Madras,  Belganm,  Allahabad,  and  Calcutta  (Alipore)  have 
been  drawn  and  found  to  resemble  each  other  closely.  All  over  India  there  was  a  minimum  between 
the  6th  and  7th,  a  maximum  about  the  18th,  another  minimum  on  the  21st,  then  a  rise,  and  a  third 
minimum  on  the  27th. 

The  first  essential  in  any  attempt  to  arrive  at  an  explanation  of  the  cause  of  the  green  sun  is  to 
ascertain  the  precise  dates  at  which  the  phenomenon  was  first  observed  in  various  parts  of  the  world.  It 
is  difficult  to  do  this,  for  peraons  are  apt  to  make  more  precise  statements  than  their  observations  warrant. 
For  instance,  the  sun  certainly  set  with  a  peculiar  silvery  gleam,  but  no  greenness,  at  Madras  on 
September  the  9th,  and  yet  many  persons  have  assured  me  that  they  saw  it  set  green  there  on  that 
evening.  The  reason  evidently  was  that  after  their  attention  had  been  arrested  by  the  green  sunsets 
of  the  10th  and  11th  they  remembered  having  noticed  something  peculiar  about  the  sunset  on  the  9th, 
and  immediately  concluded  that  the  sun  had  been  green  on  that  occasion  also.  In  consequence  of  this 
tendency  of  the  mind,  the  evidence  for  all  the  dates  given  has  been  carefully  tested,  and  has  been  found 
in  all  cases  sufficient  to  justify  the  opinion  that  these  dates  are  correct. 

It  appears  that  in  Ceylon,  in  the  south  part  of  the  Madras  Presidency,  and  at  Ongole  in  the 
north,  the  sun  was  first  observed  to  be  green  on  the  evening  of  September  9th,  and  that  over 
the  east  of  the  Presidency^  when  seen  at  all,  it  was  first  seen  green  on  the  morning  of  the 
10th.  The  green  sun  was  reported  at  Belgaum  on  the  8th,  but  although  the  observer  was  trust- 
worthy, he  did  not  make  a  note  of  the  fact  until  afterwards,  and  it  is  just  possible  that  it  may  be  a 
mistake. 

The  captain  of  the  Cleomene  reports  a  green  sun  and  moon  on  the  9th,  10th,  and  11th,  when  his 
position  was  from  lat.  8°  N.  to  lat.  16°  N.,  and  from  long.  83°  30'  E.  to  long.  88^  40'  E.  The  chief  officer 
of  the  s.s.  Pelican  saw  the  moon  greenish  on  the  night  of  the  9th,  and  the  sun  green  on  the  morning  of 
the  10th.  The  steamer  was  more  than  1000  miles  away  from  Madras,  in  lat.  10°  4'  N.  and  long.  64**  12'  B., 
wind  south-west. 

Amongst  the  instances  In  which  the  sun  has  been  observed  of  a  blue  or  green 
colour,  we  may  notice  the  following  : — 

The  sun  was  seen  blue  by  Professor  PiAZZi  Smyth  on  entering  the  Bay  of 
Palermo,  on  March  10th,  1872,  during  a  sirocco  laden  with  fine  dust.  {^) 

Dr.  BuDDE,  while  travelling  in  South  Algeria,  in  1880,  says  that  he  was  assured 
by  colonists  that  the  sun  seen  through  the  fine  dust  of  a  Sahara  wind  had  a  decidedly 
blue  colour,  a  fact  which  supports  the  view  that  the  green  sun  in  India  and  the 
paleness  of  the  sun  were  due  to  volcanic  dust  from  Krakatoa.  (**) 

RiOHTOFEN,  in  his  work  on  China  (vol.  i.,  p.  97),  notices  that  the  air  in 
Central  Asia  is  filled  with  dust,  and  that  the  sun  seen  through  it  appears  merely 
as  a  dull  bluish  disc. 

Mr.  G.  F.  Chambers,  at  the  meeting  of  the  Royal  Astronomical  Society 
January,  1884,  stated  that  the  "engineer  of  some  works  at  Eastbourne,  at  which 
large  quantities  of  sea-beach  are  crushed  by  steam  machinery,  had  inibrmed  him  that 
he  had  frequently  seen  the  sun  appear  blue  through  the  fine  dust  which  rises  into  the 

2  F 


214  MR.   E.   DOUGLAS   ARCHIBALD 

air  when  the  operations  are  in  progress.  .  .  The  sun  does  not  usually  appear  blue 
every  evening  when  it  sets,  owing  to  the  dust  particles  being  too  large,  and  because 
the  aqueous  vapour  and  other  gases  absorb  more  blue  light  than  is  dispersed  by  the 
finer  particles."* 

One  of  the  most  remarkable  observations  of  a  blue  or  green  sun,  and  one  which 
possesses  a  marked  interest  in  its  bearing  on  the  connection  between  these  phenomena 
and  the  eruption  of  Krakatoa,  is  Mr.  Wuymper's  account  (")  of  what  he  saw  duricg 
an  eruption  of  Cotopaxi  on  July  3rd,  1880. 

After  detailing  how  the  smoke  was  seen  suddenly  to  rise  from  Cotopaxi,  65  miles 
distant  from  the  party,  who  were  encamped  16,000  feet  above  the  sea  on  Chimborazo, 
he  says  : — 

"  Several  hours  elapsed  before  the  ash  commenced  to  intervene  between  the  sun 
and  ourselves,  and  when  it  did  so  we  witnessed  efTects  which  simply  amazed  us. 

"  We  saw  a  green  sun,  and  such  a  green  as  we  have  never,  either  before  or 
since,  seen  in  the  heavens.  We  saw  smears  or  patches  of  something  like  verdigris* 
green  in  the  sky,  and  they  changed  to  equally  extreme  blood-red,  or  to  coarse  brick- 
dust  reds,  and  they  in  an  instant  passed  to  the  colom:  of  tarnished  copper  or  shining 
brass.  .  .  .  The  ash  was  extraordinarily  fine.  ...  I  find  that  the  finer 
particles  do  not  weigh  the  I-25000th  part  of  a  grain,  and  the  finest  atoms  are  lighter 
still.  By  the  time  we  returned  to  our  encampment  the  grosser  particles  had  fallen 
below  our  level,  and  were  settling  down  into  the  valley  of  the  Chimbo,  the  bottom 
of  which  was  7,000  feet  beneath  us,  causing  it  to  appear  as  if  filled  with  thick 
smoke.  The  finer  ones  were  still  floating  in  the  air  like  a  light  fog,  and  so  con- 
tinued until  night  closed  in."  He  winds  up  by  saying,  "  The  changes  from  one  hue 
to  another  had  obvious  connection  with  the  varying  densities  of  the  clouds  of  wh 
that  passed.^^ 

Opinions  REOARDiNa  the  Coloured  Suns  of  1883. 

Mr.  A.  C.  Ranyakd  expresses  himself  to  the  following  effect  (^) : — 

As  to  the  suggestion  that  the  blue  suns  were  due  to  aqueous  vapour,  the 
heavens  in  such  a  case  would  be  covered  with  cloud  ;  but  the  blue  suns  are  not  described 
as  having  been  seen  through  cloud.  Many  observers  expressly  state  that  there  was 
no  cloud.  •  .  .  The  blue  colour  of  the  sun  is  easily  explained  on  physical  con- 
siderations. In  ordinary  circumstances  there  is  not  enough  dust  to  affect  the  colour 
of  the  sun ;  but  if  the  amount  were  greatly  increased,  the  intensity  of  the  dispersed 
light  would  be  increased,  and  the  blue  colour  of  the  light  dispersed  from  the  part  of 
the  atmosphere  between  us  and  the  sun  would  sensibly  affect  the  colour  of  the  sun. 

Mr.  J.  Norman  Lockyer  says  (^*) : — 

**  Theory  had  led  me  to  suspect  that,  with  the  enormous  thickness  of  air  available 

*  '  Knowledge/  March  14,  1884. 


ON  THE  COLOURED  APPEARANCES  OF  .SUN  AND  MOON.        215 

in  India^  abeorptioB  at  the  red  end  of  the  spectrum  by  aqueous  vapour  would  be  eeea 
as  well  as  the  absorption  at  the  blue,  which  is  so  common  with  us.  Seeing  the  siui 
a  vivid  green  through  th^  steam  of  the  little  paddle-boat  on  Windermere  first  led  me 
to  inquire  into  the  possibility  of  aqueous  vapour  following  the  same  law  as  that  which 
I  think  we  may  now  accept  in  the  cases  of  the  vapours  of  metals.  As  in  these 
experiments  with  vapours,  absorption  of  the  red  end  alone  was  seen,  as  well  as 
absorption  at  the  blue  end  alone,  the  assumption  that  these  two  absorptions  existed 
in  aqueous  vapour  at  once  accounted  for  the  green  sun.*' 

The  same  writer  says : — 

"  Aqueous  vapour  is  composed  of  molecules  capable  of  stopping  both  blue  and 
red  light ;  other  substances  also  will  stop  the  red.  In  ordinary  circumstances  the 
red  molecules  of  aqueous  vapour  scarcely  ever  come  into  play ;  but,  if  they  or  any 
siibstance  capable  of  acting  in  this  way  should  be  supplied,  the  sim  would  as  often 
look  green  as  it  does  now  red.'' 

Professor  Michie  Smith  says  (^) : — 

"  That  the  green  sun  is  entirely  due  to  water  vapour  I  am  not  prepared  to  affirm, 
for,  some  observations  of  Dr.  Schuster  point  to  an  influence  produced  by  suspended 
matter  in  the  air. 

**  Why  should  vapour  if  present  give  green  tints  ?  To  settle  this  point  I  made 
spectroscopic  observations,  and,  though  I  have  not  yet  reduced  them,  I  find  that  they 
indicate  a  very  marked  absorption  in  the  red  end  of  the  spectrum,  extending  nearly 
to  B,  with  a  great  development  of  the  rain-band  near  D  on  the  red  side,  accompanied 
by  a  decided  deficiency  of  the  band  on  the  green  side,  called  by  Piazzi  Smyth  *  the 
low-sim-band.'  Hence  we  have  less  red  than  usual  and  more  green.  This  is  due,  in 
part  at  least,  to  the  sun  s  light  passing  through  a  more  than  ordinary  dense  stratum 
of  aqueous  vapour,  for  we  know  that  the  thicker  the  stratum  of  vapour  the  more  is 
the  red  light  absorbed.  But  this  is  not  all,  for  we  have  quite  as  much  vapour 
without  this  green  colour ;  but  in  these  cases  the  sun  is,  I  believe,  not  seen  at  all,  but 
we  get  strips  of  green  sky,  which  are  often  seen.  The  atmosphere,  then,  I  believe, 
contains  at  present  a  large  amount  of  vapour  existing  actually  as  vapour,  and  not 
condensed  into  clouds  ;  hence  even  a  great  thickness  of  it  is  transparent,  except  to 
those  particulp^r  rays  which  aqueous  vapour,  absorbs.    . 

"  The  green  colour  can  be  seen  only  at  a  particular  altitude,  for  only  there  is 
the  thickness  sufficient  to  produce  the  necessary  absorption.  At  higher  altitudes  the 
peculiar  silvery  white  is  exactly  what  we  are  to  expect.'* 

Mr.  Henry  Cecil  asks  (^)  whether  the  green  sun,  seen  at  about  the  same  time  in 
Southern  India,  Ceylon,  and  the  West  Indies,  be  due  solely  to  the  presence  of  aqueous 
vapour,-  Is  not  the  air-  in  these  regions  noimally  surcharged  through  a  considerable 
period  of  every  year  with  aqueous  vapour  ?  And  yet  this  appearance  is  so  unusual  as 
to  create  alarm  !  .  Can,  then,  so  rare  a  phenomenon  be  due  solely  to  so  general  and 
common  a  cause  ?     When  Lockyer  saw  his  green  sun  through  the  steam  on  the 

2  F  2 


216  MR.  E.  DOUGLAS  ARCHIBALD 

boat,  were  there  not  also,  mingling  with   the  vapour,  sulphurous   fumes   from  the 

funnel  ? 

To  this  the  Editor  of  *  Nature '  appends  the  following : — 

**  The  sun  l)as  been  seen  green  through  mist  on  the  Simplon,** 

Some  account  of  experiments  and  observations  bearing  on  the  subject  of  blue  or 
otherwise  coloured  suns  will  be  found  in  the  following  papers  : — 

(1.)  "On   the  Colours  of  the   Atmosphere"    (by  Professor  Jahes  D.Forbes, 

F.RSS.  L.  and  E.,  Edinburgh,  1839),  which  includes  reference  to  numerous 

antecedent  papers  on  the  same  subject. 
(2.)  '*Note  sur  un   eflfet  de   Coloration  des  Nuages."    Par  M.   J.  Fournbt. 

1852. 
(3.)  Two  papers  by  M.  Fournett  In  the  '  Comptes  Rendus,'  vols.  xlviL  and  xlviii., 

1858   and    1859,  on  "The  EflFect  of  Aqueous  Vapour  in  causing  Blue 

Suns." 

In  the  first  of  these,  Professor  Forbes  refers  to  experiments  made  by  him  on  the 
peculiar  orange  colour  transmitted  by  steam  during  a  critical  stage  of  its  condensa- 
tion, and  attributes  the  colours  at  simset  to  the  presence  of  vapour  in  a  partially 
condensed  state.  He  only  incidentally  refers  to  the  blue  and  green  suns  of  1831, 
which  he  agrees  with  M.  Abago  in  considering  as  the  effects  of  contrast  with  an 
intensely  red  sky. 

M.  FouBNET  found  that  the  presence  of  water  vapour  imparted  to  the  atmosphere 
a  bluish  or  orange  colour.  The  phenomenon  is  seen  when  the  sun's  light  passes 
through  a  cumulus  cloud  which  increases  in  thickness  from  the  border  to  the  centre. 
It  appears  most  favourably  when  the  sun  is  hidden  by  one  cloud,  and  the  borders  of 
the  neighbouring  clouds  appear  golden  or  orange  tinted.  Between  this  orange -tin  ted 
region  and  the  sun's  disc  a  bluish  region  intervenes,  and  if  in  this  central  region  the 
Sim  itself  is  seen  through  the  cloud- veil  with  more  or  less  distinct  contour,  it  appears 
blue  or  pale  white  or  orange.* 

M.  Foubnet  apparently  attributes  this  blue  colour  solely  to  the  effect  of  contrast 
with  the  red  border. 

These  observations  leave  it  uncertain  whether  the  phenomenon  of  a  blue  sun, 
as  seen  by  M.  Fournet,  was  a  purely  transmission  effect  or  partly  one  of  contrast 
with  the  red  border ;  in  which  latter  case  the  blue  space  surrounding  it  might  have 
been  partly  a  real  colour,  due  to  diffraction.  If  the  sun  was  really  seen  blue  itself, 
both  in  these  cases  and  in  those  after  the  Krakatoa  eruption,  the  colour  must  have 
been  due  to  transmission  and  not  to  diffraction. 

Finally,  Dr.   Kiessling,  of  Hamburg,  has  made  experimentst  to  see  in  what 

•  Professor  Kiessling  in  *Met.  Zeitschrift,*  1884,  p.  119. 

t  Described  in  the  *Met.  Zeitscbrift/  Marcb,  April,  1884;  'Nature,'  vol.  xxxi.  (1885),  p.  439;  and 
in  bis  pampblet  entitled  '  Die  DammemrigserscbeinnTigen  im  Jabre  1883.' 


ON  THE  COLOURED  APPEARANCES  OF  SUN  AND  MOON.        217 

circumstances  a  coloured  sun  could  be  produced.  He  finds  water  vapour  alone,  in 
dustless  air,  ineffective.  Water  vapour  in  ordinary  dusty  air,  and  under  conditions 
which  gave  rise  to  a  foggy  condensation,  produced  transmission  tints  varying  from 
brownish-red  to  grey -blue ;  but  he  could  not,  apparently,  produce  the  green  tint 
artificially  (probably  because  the  yellow  transmissions  through  the  ordinary  lower 
atmosphere  were  not  present  in  these  laboratory  experiments). 

All  thb  leads  to  the  conclusions  which  may  be  summarized  as  follows  : — 

Summary  op  Part  IV.,  Section  I.  (c). 

(1.)  That  the  appearances  of  blue,  green,  sOvery,  and  coppery  sun,  seen  mainly 
in  the  tropical  zone  after  the  eruption  of  Krakatoa  on  August  27th,  and  sporadically 
after  its  predecessor  in  May,  1883,  were  produced  by  the  action  of  a  haze  which 
proceeded  from  the  neighbourhood  of  the  volcano,  and  was  composed  either  of  dust 
and  vapours  mixed,  or  of  dust  alone,  probably  the  former  at  first. 

(2.)  That  the  silvery  ot  pale  sun  was  seen  where  the  haze  was  most  dense  near 
the  parallel  through  Krakatoa. 

(3.)  That  the  coppdry  sun  was  seen  either  near  the  Equator,  or  where  a  narrow 
shoot  of  the  stream  occurred  towards  Japan,  and  near  the  eruption,  as  at  Teloek 
Betoeng,  from  which  it  may  be  inferred  to  have  been  caused  by  dense,  and  perhaps 
coarse,  dust  from  the  eruption,  mingled  with  lower  atmospheric  absorbing  agents. 

(4.)  That  the  blue  and  green  suns  were  seen  further  from  the  latitude  of  Krakatoa 
and  the  Equator,  where  the  stratum  was  more  attenuated. 

(5,)  That  where  the  sun  was  seen  blue  near  the  zenith,  it  frequently  became 
green  or  yellow  on  approaching  the  horizon,  and  vice  versd,  and  that  these  changes  of 
tint  were  due  to  changes  in  the  thickness  of  the  medium  and  of  the  lower  atmosphere 
traversed. 

(6.)  That  similar  appearances  have  been  witnessed  on  former  occasions  {see 
Section  V.,  p.  384),  in  association  with  accompanying  volcanic  phenomena,  and  in 
regions  where  the  air  was,  during  the  time,  charged  with  terrestrial  dust. 

(7.)  That  Professor  Kiessling,  of  Hamburg,  has  experimentally  obtained  a  blue 
sun  (1)  with  a  cloud  of  chloride  of  ammonium,  and  (2)  with  aqueous  vapour  mixed 
with  ordinary  dusty  air.* 

(8.)  That  while  in  the  tropical  zone  the  coloured  suns  occurred  for  the  first 
month  after  the  eruption  co-extensively  with  the  other  optical  eflfects,  the  sun  and 
moon  were  only  occasionally  and  temporarily  seen  green  at  a  few  places  in  the  extra- 
tropics  ;  and  in  some  of  these  it  is  not  certain  that  the  appearances  were  due  to 
anything  more  than  contrast  colours. 

E,  Douglas  Archibald. 

•  Professor  Kiessling  kindly  sliowed  these  experiments  to  tlie  writer  when  visiting  Hamburg  in 
August,  1887. 


218  MR.   E.  DOUGLAS  ARCHIBALD 


References  in  Section  I.  (c). 

Q)  *  Taglicbe  Rundschau,'  1883,  Nob.  255  and  256,  and  a  communication  to  M.  Verbeek  by  M. 
Herring,  at  Batavia. 

(»)  *  Mercantile  Record/  June  16,  1883. 

O  'Nature,*  vol.  xxix.  (1883),  p.  196. 

(*)  Colonel  J.  Stoddart,  Report,  MSS.,  April  10,  1884  {ante,  p.  116). 

(»)  *  Gold  Coast  Times,'  September  14,  1883. 

(•)  *  Nature,'  vol.  xxix.  (1884),  p.  252.     From  a  Dutch  paper.     E.  Metzger. 

(')  *  Panama  Star  and  Herald,'  *  Nature,'  vol.  xxix.  (1883),  p.  152.     Hyde  (JUrk. 

(«)  Letter  of  Hon.  Foley  C.  P.  Vereker,  of  H.M.S.  Magpie,  dated  Labnan  Island,  October  1, 1883, 

(»)  *  Hausa,'  January  2,  1884. 

(i«)  '  Ceylon  Observer,'  November  9,  1883. 

(")  Letter  from  Miss  Cathcart,  September  8,  1883. 

(")  'Nature,'  vol.  xxix.  (1883),  p.  7. 

(»)  M.  A.  T.,  'Madras  Mail,'  'Nature,'  vol.  xxviii.  (1883),  p.  577. 

(**)  C.  Michie  Smith,  *  Nature,'  vol.  xxx.  (1884),  p.  348. 

(")  C.  Piazzi  Smyth,  *  Nature,'  vol.  xxviii.  (1883),  p.  576. 

(")  'Quarterly  Journal  Royal  Met.  Society,'  vol.  x.  (1884)  p.  153. 

(")  'Nature,'  vol.  xxx.  (1884),  p.  347. 

(")  '  Nature,'  vol.  xxviii.  (1883),  p.  576. 

('•)  *  Ceylon  Observer,'  September  17, 1883. 

(»)  'Knowledge,'  March  14,  1848. 

(*»)  'Nature,'  vol.  xxix.  (1883),  p.  177. 

(«)  'Nature,'  vol.  xxix.  (1883),  p.  199. 

(^)  '  Knowledge,'  March  14,  1884. 

(•*)  'Nature,'  vol.  xxviii.  (1883),  p.  575,  and  'Times,'  December  8. 

C)  'Englishman's  Overland  Mail,'  September  23,  1883. 

(«)  '  Nature,'  vol.  xxviii.  (1883),  p.  612. 

(•)  '  Met.  Zeitschrift,'  February,  1884,  pp.  49-65. 

(^)  M.  E.  Marence,  in  '  L' Astronomic,'  by  C.  Flammarion. 

(«)  J.  Norman  Lockyer,  F.R.S.,  *  Times,'  December  8th,  1883. 

(*)  'Nature,'  vol.  xxix.  (1884),  p.  549. 

(•)  Beuf,  '  Comptes  Rendus,'  vol.  xcviii.,  pp.  498,  549. 

(')  Ship's  log,  preserved  in  the  Meteorological  Office,  London. 

(«)  "  The  Equatorial  Smoke  Stream,"  *  Hawaiian  Monthly.'     By  S.  B.  Bishop.     May,  1884. 

(»»)  '  Ceylon  Observer,'  November  2,  1883. 


ON  THE   SKY-HAZE  AND  SOME   OF   ITS   EFFECTS.  219 

PART  IV.,   SECTION  I.  (d). 

The  ''Sky-Haze"  and  some  of  its  Effects. 
By  Mr.  E.  Douglas  Archibald. 

Nearly  all  the  observers  of  the  twilight  glows,  coloured  suns,  corona,  &c.,  agree 
in  attributing  them  proximately  to  the  physical  action  of  a  peculiar  and  quite 
abnormal  cirri-form  haze  which  appeared  concurrently,  and  at  a  great  altitude,  at  first 
in  the  Indian  Ocean,  whence  it  spread  round  the  Equator,  and  ultimately  towards 
the  poles. 

It  is  especially  important  to  notice  its  earliest  appearance,  which,  like  those  of 
the  other  phenomena,  seems  to  have  occurred  shortly  after  the  minor  eruptions  of 
Krakatoa  in  May,  1883. 

Thus  on  May  26th,  from  the  log  o^  Her  Majesty,  (^)*  lat.  3°  8'  S.,  long.  90^  E.,  at 
9  p.m.,  we  hear  of  a  "  thin  haze  over  the  sky  through  which  the  larger  stars  shine.'*' 

By  itself  this  latter  observation  might  not  be  thought  to  refer  indubitably  to 
kaze  similar  to  that  which  appeared  after  August,  but  when  it  is  compared  with  the 
descriptions  of  the  latter,  and  the  "  blue  moon  seen  through  light  haze"  on  the  Belfast y 
on  July  16th  and  1 7th,  (^)  referred  to  in  Section  I.  (e),  we  can  hardly  doubt  that 
it  was  a  similar  manifestation. 

After  this,  the  next  notice  we  have  of  the  haze  was  from  the  ship  Charles 
Baly  on  August  22nd,  after  a  minor  eruption  of  Bjrakatoa,  in  which  it  reports,  in 
15°  30' S.,  lOS**  E.  (not  very  far  from  the  volcano):—" In  the  E.  and  N.K  there  was  a 
strong  white  haze  or  silvery  glare."  (^)  The  words  "silvery  glare "  are  several  times 
used  subsequently  by  other  observers. 

On  August  the  27th,  the  day  of  the  grand  eruption,  the  Barharossa,  in  2%  S., 
62*°9  K,  after  mentioning  the  unusual  silvery  sunset  on  that  day,  reports  : — "  The 
sky  was  covered  during  the  night  and  Ukewise  hazy,  although  we  had  no  signs 
ofdew."C) 

On  the  same  day  we  have  the  observation  on  ])oard  the  Sea  Witch,  when  ashore 
on  the  bar  of  Sourabaya,  Java,  of  the  sun  "  appearing  dim  and  smoky,  while  sounds  of 
heavy  cannonading  were  heard,  and  the  barometer  was  unsteady."  (*) 

On  the  same  day  the  Simla,  5°  35'  S.,  88°  K,  reports  :— "  Air  very  hazy."  (^) 

On  the  same  day  (27th)  Dr.  Mbldrum  (^)  says  that  the  sun  was  obscured  at 
Kodriguez  and  the  Seychelles,  the  sky  at  the  latter  being  reported  by  Mr.  Estridgb 
to  be  hazy  all  day,  and  followed  by  a  gorgeous  sunset.  At  the  St.  Brandon  Rocks 
"  the  sky  at  sunset  had  a  peculiar  smoky  appearance,  which  extended  nearly  to  the 
zenith  in  an  E.S.E.  direction."     At  Diego  Garcia,  from  August  27th  to  31st,  the  suu 

•  For  numbered  and  lettered  references  in  this  Section,  see  p.  230. 


220  MR.  E.  DOUGLAS  ARCHIBALD 

was  obscured  during  the  day ;  while  at  sunset  a  deep  purplish-red  glow  appeared 
until  7.15  p.m.  At  Mauritius,  on  the  27th,  the  sky  was  overcast  during  the  day  and 
the  sunset  was  smoky  in  the  west ;  and  on  the  28th  the  sunset  was  gorgeous.  On 
the  28th  the  ship  Charlotte,  r^'S  S.,  106-°2  K,  reports,  "hazy  air,"(»)  and  Captain 
LoYSEAU  of  the  Salazic,  lat.  9°  15'  S.,  long.  93°  E.,  talks  of  encountering  blinding 
showers  of  sand,  while  the  sun  was  reddish  and  the  sky  white  C) 

On  August  28  th  the  haze  continued  at  Diego  Garcia,  Rodriguez,  the  Seychelles, 
and  Mauritius,  and  was  observed  by  the  Simla,  6**  12'  S.,  88°  17'  K,  "At  2  p.m., 
sky  very  hazy,  a  fine  white  powder  falling  in  a  constant  shower  like  snow.  At 
8  p.m.,  sky  still  very  hazy  and  dust  falling."  (^) 

On  August  29th  the  Simla,  6""  26'  S.,  87""  52'  E.,  reports:— "A  very  large 
quantity  of  dust  fell  in  the  past  night.  Very  hazy  still,  and  dust  falling.  At  5  p.m., 
sun  completely  obscured  15°  above  the  horizon,  owing  to  haze  ;"  and  at  8  p.m.,  "  still 
dust."  (^)  On  the  same  day,  the  Coppename,  15°  30'  N.,  57°  30'  W.,  says  :— 
"  Clouds  appear  dry,  smoky,  and  indescribable,  at  8  p.m.  At  4  p.m.,  hot  looking 
stratus  in  N.W. ; "  (^)  and  from  August  28th  to  30th  the  Ida,  in  l-°3  N.,  108-°4  K, 
not  far  from  Java,  reports  : — "  Uninterruptedly  hazy  air.''  (•)  The  British  Empire 
2°  37'  S.,  79°  52'  E.,  also  remarks : — "A  pale  yellowish  haze  accompanying  a  fall  of 
dust  like  Portland  cement."  (*) 

On  August  30th  and  31st,  we  have  the  observation  at  Tokio,  Japan,  referred  to 
elsewhere,  of  a  "  yellowish-grey  haze."  And  on  the  latter  date  the  observations  on 
board  the  Corona,  1°  20'  S.,  21°  W., "  at  8  a.m.  a  metallic  sort  of  haze  over  sky,  sim 
shining  through  it  quite  coppery ;"  and  on  board  the  Olbers,  in  3°  5'  N.,  27°  W.,  of 
**  light  clouds  visible  towards  sundown  "  (very  similarly  worded  to  the  description  of 
the  haze  subsequently  in  the  extra-tropics). 

On  September  1st,  the  Queen  of  Cambria,  in  9°  S.,  28°  W.,  at  8  a.m.,  notices  "a 
peculiar  thin  haze  in  the  air,  through  which  the  sun  is  seen  with  a  clearly  defined 
circumference,  and  almost  white  in  colour ;  at  8  p.m.,  stars  dimly  visible  through 
haze.''  (^) 

On  September  2nd,  the  Olbers,  4°  41'  S.,  31°  10'  W.,  again  reports :—"  The 
sun  obscured  at  intervals.  At  5  p.m.,  the  sim  visible  through  clouds,  pale 
blue."  t^) 

On  the  same  day  we  hear  of  "a  long  belt  of  vaporous  sky"  at  Medellin, 
in  connection  with  the  coloured  suns  and  glows  in  that  part  of  South  America,  and 
a  pecidiar  grey  sky  through  which  the  sun  shone  faintly  was  seen  by  the 
Frieda  Grampp,  10°-2  S.,  27°'2  W. ;  the  Rosario,  3°-7  N.  ;  and  the  Argentina, 
12-°1  S.,  36°'9  W.  (•) 

On  September  3rd,  the  Queen  of  Camhna,  3°  6'  S.,  27°  4'  W.,  reports  :— **Before 
sunrise  the  haze  that  is  still  in  the  air  was  fiery  red,  and  the  sun,  when  it  appeared, 
was  of  a  dazzling  white  colour."  (^) 

On  the  same  day  the  Scotia,  1°  37'  N.,  71°  E.,  reports  "  hazy  overhead  ; "  and  on 


ON  THE   SKY-HAZE   AND   SOME   OF   ITS  EFFECTS.  221 

September  6th  the  same  ship,  5°  52'  N.,  58°  55'  E.,  reports  "  very  fine  sand  deposited 
in  places  exposed  to  the  wind."  (^) 

On  September  3rd,  the  Euterpe^  14°  S.,  7°'9  W.,  reports : — "  During  the  last  few 
days  there  is  above  the  cumulus  and  stratus  clouds  a  uniform  grey  cloud  mass  which 
frequently  covers  the  entire  sky."  (*)  A  similar  stratum  was  observed  by  the 
Argentina,  in  8°-2  S.,  34°-6  W.  («) 

From  September  1st  to  5th  we  have  the  observation,  referred  to  in  Section  I.  (k), 
of  the  "sun  being  surrounded  by  a  delicate  atmospheric  film,  through  which  the 
sun  could  scarcely  shed  its  hght,"  C^) 

On  September  4th  and  5th  a  similar  appearance  was  noticed  by  the  Euterpe 
and  Argentina,  and  by  the  Papa,  in  10°  19^  N.,  161°  21'  W.,  which  reports :— "The 
sky  in  the  morning  is  covered  with  a  thin  white  layer.  The  sim  comes  through.  The 
air  looks  yellow  and  watery."  (•) 

On  September  6th,  Eastern  time,  the  same  ship,  in  8°  l'  N.,  161°  4'  W., remarks  : — 
"  The  entire  sky  is  covered  by  an  even  yellowish-red,  high  layer  of  cirro-stratus. 
The  sun  pierces  through,  but  looks  pale,  as  when  seen  through  a  blue  glass, 
with  sharply  marked  edge,  nice  for  observations,  well  tolerable  to  the  eye,  without 
nimbus  or  halo.    At  night  the  stars  were  dimly  visible."  (•) 

Thenceforward  we  have  with  Uttle  intermission,  accounts  worded  in  very  similai' 
language,  of  the  sky  being  "  covered  with  a  light  haze ; "  (®)  "  the  sun,  when 
green,  stands  out  from  a  smoky  sky,"  S""  to  16°  N.,  87°  30'  to  88°  44'  E.  (®) 
Together  with  the  accompanying  phenomena  of  the  blue  and  green  suns,  it 
appeared  after  the  first  revolution  of  these  round  the  globe,  at  higher  latitudes 
than  on  its  first  journey.  Thus,  while  on  August  27th,  at  Mullaittivu  and  Kokkulai, 
in  Ceylon,  the  sky  was  "  murky,  and  the  rays  of  the  sun  obscured  to  the 
east,"  i}^)  it  does  not  appear  to  have  been  generally  observed  in  Ceylon,  or  to 
have  reached  Madras  and  other  places  north,  such  as  Ongole,  until  its  return  on 
September  9  th.* 

At  Ongole,  on  September  10th,  11th,  and  12th,  "the  sun  was  blue,  green, 
and  yellow.  After  sunset  a  peculiar  haze  covered  the  sky.  It  was  not  of 
suflScient  density  to  be  at  all  visible  except  where  it  reflected  the  direct  rays 
of  the  sun.  Then  it  had  a  singular  mottled  appearance,  with  a  smoky  look 
along  the  denser  portions,  suggesting  clouds  of  smoke  or  dust  in  the  upper  atmos- 
phere." (11) 

Again,  on  September  Xlth,  at  Pallai,  Ceylon,  we  hear  that  "  the  last  day  or  two 
have  proved  very  hazy,  and  the  sun  shines  with  a  bluish  tinge.  I  followed  the  large 
spot  on  the  sun  this   afternoon  without  even  the  aid   of   smoked  glass,  the  sun's 

=*  From  this  observation  it  appears  that  the  northern  edge  of  the  dnst-stream  from  Krakatoa,  just 
skirted  the  northern  edge  of  Ceylon  when  starting  on  its  first  revolation.  Krakatoa  being  in  6°  south, 
would  make  the  semi-width  of  the  stream  14°. 

2   G 


2'^2  MR.   B.   DOUGLAS  ARCHIBALD 

brightness  being  so  dimmed  by  the  dense  masses  of  blue  haze  in  which  he  eventually 
disappeared."  (^^) 

A  communication  from  an  observer  in  10°  48'  N.,  78°  52'  E.,  September  10th, 
states  that  "  The  sun  was  shining  with  a  subdued  light  in  a  distant  and  hazy,  but 
otherwise  cloudless,  sky.  It  could  be  looked  at  steadily  with  the  naked  eye.  The 
appearance  was  decidedly  as  if  the  ordinary  sun  was  screened  off  by  a  thick  stratum 
of  vapour  which  cut  off  some  of  the  component  rays  of  white  light  and  made  it  look 
green."  (») 

At  Poudicherry,  September  12th,  **  This  is  the  third  time  the  sun  has  been 
dimmed.  It  is  as  if  it  were  covered  with  a  thin  gauze  veil  of  tender  Prussian 
blue."  (A*) 

It  also  seems  to  have  lasted  in  these  places  for  some  considerable  time.  Thus, 
Mr.  Parker,  at  Hambantota,  Ceylon,  says,  October  11th  : — "There  is  still  haziness 
night  and  morning.  In  the  morning  for  about  an  hour  and  a  half  after  sunrise,  and 
in  the  evening  for  a  similar  length  of  time."  (*^) 

The  same  stratum  afterwards  spread  over  extra-tropical  regions,  and  was 
chiefly  observed  by  Messrs.  Russell,  Perry,  Bozward,  and  Glydk,  in  England, 
and  MM.  Krone,  Thollon,  Ricjcd,  Janbsch,  Pockels,  and  Lecher,  on  the  Con- 
tinent. 

The  Hon.  Rollo  Russell,  who  observed  the  phenomenon  very  closely,  thus 
describes  its  second  appearance  near  London  on  November  9th : — "  There  was  a 
slight  haze  on  the  horizon  at  sunset,  having  a  greenish-white  and  yellowish-white 
opalescence  at  its  upper  border.  About  15  minutes  after  sunset  the  sky  was  pink, 
and  below  the  pink  a  shining  green  and  white  opalescence,  like  a  luminous  mist. 
The  coloured  portion  of  the  sky  was  fan -shaped  and  resembled  a  very  high  thin 
filmy  cirrus.  .  .  .  The  illuminated  portion  seemed  not  to  belong  to  clouds 
but  to  glow  of  itself,  like  some  super-atmospheric  film;  and  yet  the  idea  of 
an  extra  atmospheric  cause  could  not  be  entertained  consistently  with  its  later 
behaviour."  ('*) 

Herr  Pockels,  in  Brunswick,  writing  December  31st,  states  that  after  the  glows 
of  November  27th,  28th,  and  29th,  **The  almost  cloudless  sky  was  covered  with 
exceedingly  filmy,  wavy,  and  woolly  clouds,  which  could  be  seen  only  near  the 
sun."  07) 

Mr.  Glyde  (Torquay)  speaks  of  it  as  "  a  greyish  mist,  but  tinted  pink  near 
the  sun,  and  covering  the  sky  all  day.  It  was  higher  than  the  most  elevated 
cirrus."  {^^) 

Professor  O.  N.  Stoddard  (Wooster,  Ohio)  says  that  it  is  "not  an  ordinary 
cirrus-cloud."  (^®) 

Prof.  Hazen,  in  Washington,  speaks  of  the  sun,  in  an  otherwise  cloudless 
sky,  "  as  shining  through  a  dense  haze ; "  a  similar  haze  being  seen  round  the 
moon.  (^^) 


ON  THE  SKY-HAZE  AND   SOME  OF  ITS   EFFECTS.  223 

Rev.  S.  J.  Perry,  F.R.S.  (Stonyhurst),  says  that  the  haze  "  bore  no  resemblance 
to  ordinary  haze/*  (^^) 

M.  Thollon  observed  the  same  haze  at  Nice  from  November,  1883,  onwards, 
and  attributed  to  it  the  coronas  round  the  siin  and  moon,  as  well  as  the  lack  of 
definition  in  astronomical  observation.  (^^) 

Professor  A.  Ricc6,  of  Palermo,  speaks  to  the  same  eflTect,  and  describes  the 
haze  as  being  "minutely  and  irregularly  channelled,  as  if  composed  of  cirro- 
strati."  n 

M.  C.  MousELLE,  of  Auteuil,  photographed  the  vicinity  of  the  sun  in  1884,  and 
says  : — "These  photographs  show  a  corona  of  diffused  hght  about  it,  the  intensity  of 
which  depends  in  part  on  the  degree  of  transparency  of  the  very  filmy  clouds,  having 
a  hazy  or  stratified  appearance,  and  which  seemed  to  be  the  sole  or  principal  cause  of 
the  corona." 

The  similarity  of  the  foregoing  to  the  remarks  of  observers  within  the  tropical 
zone  is  suflficiently  obvious,  and  raay  be  further  corroborated  by  a  perusal  of  the  Table 
of  First  Appearances  in  Section  II.,  p.  263. 

Peculiar  Features  of  the  Haze. 

(1.)  There  seems  to  have  been  a  difference  in  the  quality  of  the  haze  as  it  was 
first  seen  near  the  Equator,  and  more  especially  in  the  Indian  Ocean,  and  as  it  after- 
wards appeared  in  higher  latitudes. 

Thus,  in  the  former  regions  the  haze  seems  to  have  been  yellow,  reddish,  smoky, 
or  white,  to  have  covered  the  entire  sky,  and  to  have  been  visible  at  midday, 
and  it  is  only  in  these  regions  that  it  appears  to  have  been  thick  enough 
to  cut  off  some  of  the  component  colours  of  the  spectrum,  and  produce  blue  and 
green  suns  at  high  altitudes.  In  these  regions  it  was  also  dense  enough  to  hide  the 
sun  entirely  when  the  latter  was  within  a  few  degrees  of  the  horizon. 

On  the  other  hand,  in  higher  latitudes  it  appears  to  have  been  generally  thinner, 
only  partially  visible  and  more  like  a  gauzy  cirro-stratus. 

Thus  Professor  Stoddard,  in  Ohio,  says  : — "  It  was  invisible  everywhere  except 
near  the  sun  ; "  and  Mr.  N.  S.  Shaler  *  speaks  to  a  similar  effect. 

Mr.  Bishop  says  : — "  Even  at  Honolulu  it  was  always  perfectly  transparent  and 
invisible  except  under  certain  conditions." 

The  Hon.  Rollo  Russell  says : — "  It  is  visible  (except  when  very  dense  or  in 
the  neighbourhood  of  the  sun)  only  about  the  time  of  sunrise  and  sunset.  During  the 
day  not  the  faintest  trace  obscures  the  clear  azure,  whereas  ciiTus  becomes  more 
distinct  with  more  daylight."  (^) 

In  England,  then,  the  haze  was  probably  too  thin  to  produce  coloured  suns,  but 

*  *  AtlanUc  Monthlj/  April,  1884. 
2  G  2 


224  MR.  E.   DOUGLAS   ARCHIBALD 

thick  enough  to  be  seen  and  to  cause  a  glow  by  reflection,  when  the  solar  rays  fell 
upon  it  at  a  small  incident  angle. 

It  is  scarcely  necessary  to  remark  that  the  thinning  off  of  the  haze  in  the  extra- 
tropics  is  exactly  what  might  have  been  expected  if  it  had  its  source  near  the 
Equator,  while  the  march  westward,  conciurently  with  the  other  optical  effects,  which 
it  cannot  be  doubted  were  proximately  due  to  it,  leads  us  back  to  the  Indian  Ocean 
as  the  source,  and  August  27th  as  the  dat«,  of  its  first  appearance  in  any  great 
quantity. 

(2.)  It  had  generally  a  rippled  or  striated  structure,  somewhat  analogous  to  cirrus 
or  cirro-stratus. 

Several  observers  testify  to  this,  including  Messrs.  Perry,  Bishop,  Rioo6,  Sealer, 
Russell,  Rebeur-Pasohwitz,  Bozward,  Krone,  and  G.A.N.  ("),  and  it  seems  to 
have  been  noticed  from  the  very  first.  Thus,  in  3°'2  S.,  16°"4  W.,  the  s.s.  Carola 
notes  that  "  the  atmosphere  appeared  to  be  full  of  very  small  uniformly  distributed 
clouds."  (•) 

The  Rev.  S.  E.  Bishop  talks  of  "  a  wavy  ripple  "  observable  in  its  structure. 

Mr.  Shaler,  in  the  'Atlantic  Monthly,'  remarks  that  the  haze  is  "stratified;" 
and  Dr.  Rebeur-Paschwitz,  on  December  18  th,  notices  "strise  dipping  at  different 
angles."  {'') 

The  Hon.  Rollo  Russell,  who  carefully  observed  the  haze  very  closely  in 
Surrey,  says  that  it  was  more  analogous  to  cirro-stratus  than  cirrus,  but  to  cirro- 
stratus  seen  at  a  distance,  for  cirro-stratus  seen  overhead  presents  features  not  seen  in 
the  cloud-haze.  In  fact,  none  of  the  icsiuil  characteristics  of  the  highest  clouds  were 
apparent  in  the  earlier  phenomena  of  November  and  December,  1883.  The  haze 
usually  resembled  simply  a  haze  or  smoke,  in  bands  of  greater  and  less  density, 
without  Jibres  or  angles,  but  later  on,  some  cross  striations  became  visible  in  the 
bright  part  of  the  sky  after  sunset,  and  these  closely  resembled  the  striated  cirro- 
stratus.  At  a  distance,  i.e.,  when  seen  on  the  horizon,  the  resemblance  to  cirro- 
stratus  seems  to  have  existed  fi'om  the  first  in  the  tropics.  The  total  absence  of 
cirrus  forms,  such  as  mares'  tails,  is  remarkable. 

Again,  he  observes : — "  It  showed  the  sort  of  stratification  in  thin  streaks,  which 
often  appears  in  cirro-stratus,  but  its  elevation  was  evidently  greater  than  that 
common  to  this  cloud."  (**) 

This  stratification  was  not  constant,  and  on  some  days  the  structure  was 
amorphous. 

Messrs.  Russell,  Shaler,  and  Bozward  testify  to  a  motion  being  observable 
in  the  streaks,  though  they  differ  widely  in  their  estimates  of  such  motion, 
the  two  latter  making  the  streaks  move  rapidly  in  a  north-east  direction,  while  the 
former  only  once  or  twice  observed  an  apparent  and  very  slow  movement  eastwards 
after  long  watching  on  several  occasions. 

Accoixiing  to  the  Hon.  Rollo  Russell,  the  direction  or  axes  of  the  streaks 


ON  THE  SKT-HAZE   AND    SOME   OF   ITS   EFFECTS.  225 

generally  lay  south-west  to  north-east,  both  in  England  and  in  Italy.  Professor 
Ricc6  confirms  this,*  as  well  as  the  indications  of  a  motion  in  the  same  direction. 

(3.)  Its  presence  peculiarly  afiected  astronomical  definition. 

On  this  point  we  have  pretty  general  testimony,  including  that  of  Messrs. 
Saxby  r),  F.RA.S.  (^),  W.  C.  WiNLOCK,t  Krone,  Piazzi  Smyth,  &c. 

Mr.  Saxby  says  : — "An  auroral  haze  of  similar  appearance  to  the  red  sunset  haze 
will  often  improve  the  definition  of  celestial  objects,  but  this  haze  shows  a  decidedly 
opposite  tendency ;  and  a  Herculis  was  so  blurred  as  to  be  scarcely  recognisable  at 
altitudes  at  which  any  ordinary  haze  would  have  transmitted  a  tolerable  result." 

It  was  found,  by  the  party  deputed  by  the  Royal  Society  to  photogi'aph  the 
solar  corona  on  the  Riffel,  under  the  charge  of  Mr.  C.  Ray  Woods,  that  the  year 
1884  was  exceptionally  unfavourable  for  the  work,  "in  consequence  of  an  unusual 
want  of  transparency  in  the  higher  regions  of  the  atmosphere,  this  made  it  impossible 
for  Dr.  HuGGiNS  to  obtain  any  photographs  of  the  corona  that  year  in  England."(^) 

Mr.  John  Ballot,  in  the  Transvaal,  noticed  on  the  7th  April,  1884,  that  "the 
sky  seemed  clear  and  the  stars  bright,  but  on  using  the  6-inch  on  Jupiter,  the  planet 
presented  most  of  the  time  just  a  luminous  blurr  with  spurious  images  flapping  on  its 
sides,  which  seemed  to  me  to  be  caused  by  the  glow-producing  medium.*'  (*^) 

Dr.  Krone  noticed  that  at  midnight  the  haze  obscured  all  stars  below  the  4th 
or  5th  magnitude  (*^),  and 

Mr.  WiNLOCK  reports  : — **  Stars  of  the  3rd  or  4th  magnitude,  which  have 
frequently  been  seen  on  a  good  observing  day,  it  is  almost  useless  to  try  for  now,  the 
phenomenon  is  evidently  not  local." 

(4.)  The  peculiar  efiects  witnessed  during  subsequent  lunar  eclipses. 

There  have  been  since  September,  1883,  only  two  total  eclipses  of  the  moon,  and 
there  was  one  large  (0*88  of  moon's  diameter)  partial  one. 

Of  the  first,  April  9th,  1 8  8  4,  no  record  has  been  found.  The  second,  that  of  October 
4th,  1884,  attracted  considerable  attention  from  the  abnormal  obscurity  of  the  moon. 
The  facts  are  given  at  large  in  several  papers  in  the  *  Monthly  Notices '  of  the  Royal 
Astronomical  Society,  but  the  following  extracts  sufficiently  indicate  its  exceptional 
character : — 

Total  Eclipse  of  the  Moon,  October  ith,  1884. 

Bodcliffe  Obs.,  Oxford.— M.r.  E.  J.  Stone,  M.A.,  F.R.S.,  saysj:— "The  eclipse 
was  much  the  darkest  that  I  have  ever  seen." 

Dun  JEcht. — Mr.  J.  G.  Lohse  says  : — "  During  the  totality  the  moon  was  very 
faint,  and  the  copper  tint,  so  conspicuous  in  other  eclipses,  was  seen  only  occasionally, 
and  then  only  faintly." 

*  In  his  paper  quoted  in  Sections  I.  (b)  and  I.  (e). 

t  "  The  Long-continued  bad  Seeing,"  *  Science,'  vol.  iv.,  1884,  pp.  94,  96. 

X  *  Monthly  Notices,'  vol.  xlv.,  p.  34. 


226  MR.   E.   DOUGLAS   ABC^HIBiLLD 

Stonyhurgt. — The  Rev.  S.  J.  Pkrey,  F.R.S  ,  says  : — ''  The  usual  copper  tint  of  the 
eclipsed  moon  was  not  perceived  except  towards  the  close  of  the  eclipse,  and  then  it 
was  only  very  slight."  ^ 

Bristol.— Kt.  W.  F.  DsNNrNO  says : — *'  The  most  noteworthy  feature  in  con- 
nection with  the  phenomenon  was  that  the  moon  at  the  total  phase  appeared  far 
less  luminous  than  usual."  .  .  .  .  '^  The  firmam^it  grew  dark  as  on  an  ordinary 
night  when  the  moon  is  entirely  absent." 

Bridpoi'L — The  Rev.  S.  J.  Johnson  says : — **  At  9  h.  10  min.,  the  whole  of  the 
lunar  circle  began  to  be  seen  through  the  telescope,  but  without  a  trace  of  the 
ordinary  coppery  redness — to  quote  Keplbb,  respecting  the  lunar  eclipse  of  June, 
1620 — ^wie  omni  nibedine."* 

Clapham,  London. — Mr.  Edmund  J.  Spitta*  says : — "  During  totality  the  moon 
was,  generally  speaking,  exceedingly  faint — indeed,  at  times  barely  visible  to  the 
naked  eye — and  presented  none  of  the  coppery  colour  usual  on  those  occasions." 

The  only  other  subsequent  lunar  eclipse  of  importance,  that  of  March  30th, 
1885,  was  not  visible  in  this  country,  but  was  observed  in  Tasmania  by  Mr.  A.  B. 
BiGGS.(^')  He  says  that,  at  the  time  of  maximum  eclipse,  "All  within  the  shadow 
was  utterly  obliterated — ^lost  in  the  dead  slaty  tint  of  the  sky.  I  could  not 
distinguish  a  single  crater  after  once  it  was  fairly  within  the  shadow.  Not  the 
^lightest  trace  of  the  coppery  tint  was  visible  throughout." 

This  peculiar  absence  of  the  coppery  tint  ordinarily  visible,  and  m  circumstances 
which  are  described  as  having  been  very  favourable  for  observation,  "  the  sky  being 
free  from  clouds,  and  the  moon  in  full  view  during  the  whole  period  of  the  eclipse," 
seems  to  favour  the  notion  that  the  haze  not  only  exerted  a  general  absorption,  but, 
as  the  appearance  of  the  blue  and  green  suns  show,  a  selective  absorption,  more 
especially  of  the  red  end  of  the  spectrunut 

(5.)  The  radiant  point  of  the  wisps  or  streaks  of  the  haze  when  the  glows  were 
at  their  best,  and  the  structure  of  the  haze  when  noticeable,  lay  apparently  some 
distance  below  the  horizon. 

This  was  particularly  observed  by  the  Hon.  Kollo  Russell. 

(6.)  Though  somewhat  analogous  to  cirrus,  the  streaks  of  haze  never  presented 
a  curled  or  twisted  appearance,  but  were,  apparently^  long  parallel  bands. 

•  *  Montlilj  Notices,  Boy.  Aat.  Soc.,'  vol.  xlv.,  p.  154. 

t  [Since  this  was  in  type  an  article  by  Professor  Dufoue  has  appeared  in  Flammaeiok's 
*  rAstronomie '  (January,  1888),  in  which  he  strongly  supports  the  theory  that  the  almost  complete 
invisibility  of  the  moon  in  18d4>  was  due  to  Krakatoa  dnst,  and  he  refers  to  M.  Flahmariok  ha\ring 
expressed  the  same  view.  On  turning  to  M.  Flammabion's  original  statement  (*  TAstronomie,*  1884, 
p.  407),  it  will  be  found  that  he  refers  to  the  eclipses  of  April  25, 1642,  May  18, 1761,  and  June  10, 1816, 
as  previous  analogous  cases.  On  comparing  these  and  that  of  1620,  observed  by  Kepler,  with  Part  lY., 
Sec.  v.,  of  this  volume,  it  will  be  found  that  in  each  of  these  four  instances  there  had  been  an  eruption 
in  the  previous  year — that  of  1815  being  the  great  one  of  Tomboro. — Eo.] 


ON  THE   SKY-HAZE  AND   SOME   OF   ITS   EFFECTS.  227 

This  was  generally  observed,  and  appears  to  indicate  that  the  haze  was  at  too 
great  an  elevation  to  be  affected  by  the  vertical,  or  other  movements,  which  accom- 
pany cyclonic  and  anti-cyclonic  systems  at  lower  altitudes. 

(7.)  At  sunset  the  haze  began  to  shine  with  a  red  light  soon  after  the  cirrus  had 
ceased  to  shine ;  about  20  minutes  according  to  the  Hon.  Ex)LLO  Russell, 

(8.)  It  had  a  definite  lower  boundary.     (Aitken.)* 

This  also  was  noticed  by  Mr,  BiSHOP.f 


Sbculab   Dubation. 


The  cloud-haze  not  being  so  conspicuous  as  some  of  the  other  phenomena, 
except  near  its  origin  within  the  tropical  belt,  has  not  been  so  closely  observed. 
At  first  it  was  seen  generally  throughout  the  tropics  in  connection  with  the  coloured 
suns,  corona,  and  twilight  glows,  and  subsequently  with  the  two  latter  in  the  tem- 
perate zones.  In  the  former  region  it  was  distinctly  noticeable,  apart  from  the 
attendant  optical  phenomena.  In  the  latter,  it  was  noticed  at  first  only  near 
sunrise  and  sunset  in  connection  with  the  twilight  glows ;  but  subsequently  it 
was  noticed  more  generally  in*  connection  with  the  corona  surrounding  the  sun 
in  the  daytime. 

The  Hon.  Eollq  Eussell,  at  Richmond,  Surrey,  when  observing  the  glows,  and 
writing  on  January  22nd,  1884,  says; — "It  has  been  visible  on  every  clear  day  for 
more  than  two  months,  and  has  been  quite  independent  of  wind  and  weather." 

The  same  observer,  when  in  Italy  between  January  3rd  and  4th,  says : — "  The 
intensity  or  thickness  of  the  reflecting  stratum  was  certainly  much  less  than  at  the 
end  of  November."  Further  on  he  says  : — "In  the  glows  of  December,  1883,  and 
January,  1384,  the  m^-tter  concerned  seemed  to  become  thinner." 

The  Rev.  S,  E.  Bishop,  writing  from  Honolulu  in  April,  1884,  says: — "The 
haze,  with  its  glows  and  opslescenfc  corona  round  the  sun,  is  still  being  constantly 
seen."  {«) 

After  this  we  do  not  hear  much  of  the  haze  independeniily  of  the  other 
phenomena,  though  it  certainly  continued  to  be  seen  whenever  the  conditions  were 
favourable  for  a  twilight  glow,  while  its  prolonged  presence  is  attested  by  various 
observations — ^spectroscopic,  astronomical,  and  polariscopic. 

Like  the  corona,  it  survived  in  a  modified  form  the  more  brilliant  phases  of 
tlie  twilight  glows ;  and,  like  it,  appears  to  have  become  almost  imperceptible  towards 
the  close  of  1885. 

*  Second  note  on  remarkable  sunsets,  *  Proc.  Royal  Soc.  Edin./  1883-84. 
t  *  American  Met.  Journal,'  August,  1886,  p.  129. 


228  MR.   E.  DOUGLAS   ARCHIBALD 


The  Connection  of  the  Sky-Haze  with  the  Erufhon  of  Krakatoa, 

The  remarkable  haze  which  we  have  juBt  described,  and  to  the  peculiar  physical 
properties  of  which  the  other  optical  effects  are  attributed,  both  by  those  who  only 
casually  observed  them  and  by  those  who  subjected  them  to  a  more  prolonged 
scrutiny  and  analysis,  appears  to  have  been  nothing  more  or  less  than  the  smoke 
(so-called)  of  the  eruption,  attenuated  into  a  semi-transparent  film. 

It  appears  to  have  been  manifested  sporadically  after  the  May  eruption,  as  well 
as  generally  after  that  in  August,  the  observation  on  Her  Majesty  on  May  26th,  1883, 
in  3°  8'  S.,  90°  E.,  at  9  p.m.,  of  "  a  thin  haze  over  sky  through  which  larger  stars 
shine/'  being  worded  very  similarly  to  those  which  were  noted  afterwards  in  such 
abundance. 

In  many  oases  in  the  Indian  Ocean  it  was  reported  simultaneously  with  falls 
of  dust  on  ships  ;  and  in  most  cases  wherever  it  appeared,  especially  in  the 
Indian  Ocean,  it  was  accompanied  by  coloured  or  silvery  suns  and  by  glows  at 
twilight. 

On  the  other  hand,  there  are  few  detailed  accounts  in  which,  where  glows,  &c., 
appeared,  either  haze  or  a  lofty  cirro-stratus,  or  a  delicate  atmospheric  semi-trans- 
parent film,  or  a  "  peculiar,"  "  smoky,"  and  "  indescribable  *'  cloud-stratum  is  not 
mentioned  as  a  concomitant. 

For  the  first  two  or  three  days  after  the  eruption  which  ended  on  August  27th, 
it  appeared  over  the  groups  of  islands  in  the  south-west  part  of  the  Indian  Ocean, 
represented  by  Diego  Garcia,  the  Seychelles,  St.  Brandon,  Rodriguez,  and  Mauritius, 
and  by  the  ships  Barbarossa,  Simla,  Charlotte,  Salazic,  British  Empire,  Scotia,  and 
Ida — the  former  representing  an  area  embracing  20^  of  longitude  and  20^  of  latitude, 
and  the  latter  a  different  one  covering  29^  of  longitude  by  14®  of  latitude,  and 
between  them  the  larger  part  of  the  Indian  Ocean.  Later  on  we  hear  of  its  being 
observed,  like  the  other  phenomena,  not  only  over  widely  distant  localities  along  the 
equatorial  belt,  but  for  days  together  through  considerable  ranges  of  latitude  by  the 
Queen  of  Cambria  and  Olbers  in  the  Atlantic,  and  the  Papa  in  the  Pacific,  showing 
it  to  have  been  of  fairly  uniform  extension,  as  well  as  of  general  occurrence. 

The  remarks  on  board  the  Corona  on  August  31st,  and  Queen  of  Cambria  on 
September  1st,  in  particular,  are  clear  in  showing  its  appearance  in  the  Atlantic  area 
soon  after  its  general  spread  over  the  tropical  part  of  the  Indian  Ocean,  to  have  been 
of  a  precisely  similar  character  to  that  observed  in  the  latter  ocean,  and  the  following 
observation  on  the  latter  ship  on  September  13th,  in  14°  N.,  26°  42'  W.,  accentuates 
this  general  uniformity  as  well  as  peculiarity  of  appearance  : — "  I  don't  know  what 
to  call  the  stuff  that  is  seen  in  the  upper  regions,  thin  cirro-stratus  or  haze ;  it 
was  like  that  seen  south  of  the  Equator,  first  early  on  September  1st  and  last  on 
September  5th." 


ON   THE   SKY-HAZE   AND   SOME  OF  ITS   EFFECTS.  229 

That  the  haze  was  the  proximate  cause  of  all  the  other  optical  phenomena  is 
amply  testified  to,  both  by  the  direct  statements  of  observers,  some  of  which  we  have 
quoted  in  the  present  section,  and  also  by  numerous  cases  in  which  its  presence  is 
indirectly  associated  with  that  of  several  of  the  other  phenomena. 

This  fact  being  once  established,  forms  one  of  the  strongest  arguments  in  favour 
of  the  dependence  of  all  the  optical  phenomena,  following  both  the  minor  and  the 
major  eruptions  of  Ejrakatoa,  upon  the  finer  material  ejected  during  those  outbursts. 
Moreover  it  is  plain  fi-om  the  earlier  records,  some  of  which  are  quoted  in  Section  II., 
p.  264,  that  the  haze  began  close  to  where  the  thick  voliunes  of  smoke,  seen  near 
the  volcano,  ended. 

Mr.  Elleby,  F.R.S.,  of  Melbourne,  and  one  or  two  other  writers,  suggest  that  the 
haze  itself  may  have  been  a  secondary  chemical  or  physical  effect  of  the  eruption ; 
but  there  does  not  seem  to  be  any  evidence  to  show  that  the  intrusion  of  volcanic 
ejectamenta  into  the  atmosphere  would  introduce  notable  chemical  changes  into  its 
composition,  or  that  these  would  extend  over  a  wider  area  than  that  embraced 
by  the  ejectamenta  themselves. 

Summary  of  Part  IV.,  Section  I.  (d). 

The  preceding  paragraphs  present  an  outline  of  the  chief  facts  in  connection  with 
the  cloud-haze,  and  lead  to  the  following  conclusions  : — 

(1.)  That  soon  after  the  grand  eruptions  of  Krakatoa  on  August  26th  and  27th, 
a  remarkable  dimming  of  the  sun  took  place  in  the  immediate  neighbourhood  of  the 
volcano,  together  with  haze  and  fctlls  of  dust  on  ships,  which  in  one  case  (the  Scotia, 
September  8th,  in  lat.  lO""  N.,  long.  53°  E.,  "  still  a  deposit  of  sand  found  ")  extended 
no  less  than  62°  to  the  westward,  and  more  than  3,700  English  miles  from  the  volcano. 

(2.)  That  this  haze  was  propagated  mainly  westwards,  concurrently  with  the 
other  optical  phenomena,  from  the  neighbourhood  of  Java.  (In  Section  III.  (c),  p.  337, 
the  exact  rate  of  transmission  is  worked  out.) 

(3.)  That  most  observers  agree  in  considering  it  to  be  the  proximate  cause  of 
the  other  optical  effects,  including  the  twilight  glows,  coloured  suns,  and  large 
corona. 

(4.)  That  it  was  densest  in  the  Indian  Ocean  and  along  the  equatorial  belt,  where 
it  was  often  thick  enough  to  hide  the  sun  entirely  when  within  a  few  degrees  of  the 
horizon,  besides  sensibly  colouring  its  rays  when  at  greater  altitudes.  In  the  extra* 
tropics  it  was  much  less  dense,  and  was  generally  visible  only  at  sunrise  and  sunset ; 
though  even  there  it  peculiarly  affected  astronomical  definition  in  a  manner  different 
from  ordinary  aqueous  haze. 

(5.)  That  while,  in  some  of  its  features,  it  partook  somewhat  of  the  character  of 
a  lofty  cirrus  or  cirro-stratus  cloud,  it  yet  differed  in  many  respects  from  an  ordinary 
aqueous  cirrus. 

2  H 


230  MB.  B.  DOUGLAS  ARCHIBALD 

(6,)  That  it  appeared  to  be  far  above  ordinary  cirri,  and  exhibited  an  absence  of 
the  curls  and  twists  by  which  such  clouds  are  usually  characterised,  and  which  are 
usually  attributed  to  local  atmospheric  movements  at  their  level.  (Its  height  being 
that  deduced  in  Section  IV.,  p.  340.) 

(7.)  That  while  it  was  at  a  height  where  the  temperature  is  always  far  below  the 
freezing  point  of  water,  no  trace  of  true  ice-halos  was  observed,  and  that  while  it 
produced  some  effects,  such  as  coloured  suns  and  glows,  which  might,  in  certain  cir- 
cumstances, have  been  caused  by  aqueous  vapour,  the  general  evidence  shows  that  it 
contained  something  besides  ordinary  aqueous  vapour,  and  that  it  was  either  entirely 
fine  dust  or  a  mixture  of  frozen  vapour  of  water  or  other  substances  with  dust. 

(8.)  That  the  spectroscopic  evidence  referred  to  in  Sections  I.  (c),  p.  199,  and 
I.  (e),  p.  231,  tends  to  show  that  the  haze  was  not  gas,  but  a  cloud  of  solid  particles, 
either  ice  or  dust,  which  at  first  cut  off  the  red  end  of  the  spectrum  relatively  more 
than  the  violet,  and  subsequently  exercised  a  general  absorption,  which  was  more 
noticeable  in  the  less  intense  rays  at  each  end,  than  towards  the  middla 

(9.)  That  it  appeared  on  former  occasions  (1783  and  1831)  in  association  with 
pale  suns  and  twilight  glows,  which  were  at  that  time  ascribed  to  contemporaneous 
eruptions. 

E.  DouQLAS  Abchibald. 


ON  THE    SKY-HAZE  AND  SOME  OF  ITS  EFFECTS.  231 


References  in  Section  I.  (d). 

(*)  All   obserYations  referred  to    thns  are  taken  from    Dr.  Nemnajer's   article  in  tlie   'Met. 

Zeitschrift,'  February,  1884. 

C)  All  obseryations  referred  to  thus  are  from  ships*  logs  preserved  in  the  London  Meteorological 
Office. 

O  '  Ceylon  Observer,'  October  12, 1883. 

O  *  American  Journal  of  Meteorology,'  vol.  i.,  May,  1884. 

C)  'Proc.  Roy.  Met.  Soc.,  Mauritius,'  May  22, 1884. 

C*)  *  Comptes  Rendus,'  vol.  xovii.  (1883),  p.  1101. 

C)  '  Ceylon  Observer,'  October  2,  1883, 

C)  *  Japan  Gazette,'  September  21, 1883. 

O  'Nature,'  vol.  xxix.  (1884),  p.  366. 

O  *  L'Astronomie,'  Flammarion,  February  1, 1884. 

C)  *  Honolulu  Advertiser.' 

(•)  *  Indian  Daily  News,'  September,  1883. 

O  Colonel  J.  Stoddart,  MSS.  BepoH,  April  10, 1884.     (See  p.  116  et  seq.) 

(")  '  Nature,'  vol.  xxviii.  (1883),  p.  576. 

(»)  '  Ceylon  Observer,'  September  15, 1883. 

C*)  *  Ceylon  Observer,'  October  26,  1883. 

C*)  •  Ceylon  Observer,'  September  21,  1883. 

(^)  H.  Parker.    MSS.  Letter  dated  Hambantota,  November  18,  1883. 

(")  '  Quarterly  Journal,  Royal  Met.  Society,'  vol.  x.  (1884),  p.  139. 

(")  •  Met.  Zeitsohrift,'  March,  April,  1884. 

CO  '  Standard,'  December  26, 1883. 

C*)  '  Nature,'  vol.  xxix.  (1884),  p.  356. 

(*)  *  American  Journal  of  Science,'  vol.  xxviii.,  March,  1884. 

(^)  MSS.,  dated  Stonyhurst,  March  6, 1884. 

(»)  <  Comptes  Rendus,'  vol.  xoviii.,  p.  760. 

C")  •  Comptes  Rendus,'  vol.  xcviii.  (1884),  p.  1299. 

(»*)  '  Quarterly  Journal  Royal  Met.  Society,'  voL  x.  (1884),  p.  139. 

C*)  '  Science,'  vol.  iii.  (1884),  p.  4. 

C^)  '  Met.  Zeitsohrift,'  March,  April,  1884. 

(")  *  Observatory,'  vol.  vii.,  p.  19. 

("•)  •  English  Mechanic,'  June  20, 1884. 

(«•)  '  AthensBum,'  May  9,  1885,  p.  602. 

C')  *  English  Mechanic,'  May  29,  1884. 

(")  *  Launceston  Examiner,'  Tasmania,  April  1,  1885. 

(»)  *Met.  Zeitsohrift,'  July,  1884. 

(^  '  Hawaiian  Monthly,'  May,  1884. 


2  h2 


232  MR.  E.  DOUGLAS  ARCHIBALD 

PART  IV.,  SECTION  I.  (b). 

The  large  Corona  round  the  Sun  and  Moon  in  1883-4-5,  generally  known 

AS  ''Bishop's  Ring." 

By  Mr.  E.  Douglas  Archibald. 

With  the  possible  exceptioQ  of  some  observations  on  board  the  Belfast,  between 
16^  31'  S.,  31°  40'  W.,  and  11°  3'  N.,  and  85°  53'  E.,  from  May  26th  to  July  17th,  1883, 
the  first  indications  of  this  phenomenon  were  observed  immediately  after  the  great 
eruption  of  Krakatoa  in  August,  1883,  and  it  continued  visible  until  the  spring  of  1886. 

After  the  grand  eruption,  on  the  27th  of  August,  1883,  the  first  notice  we 
have  of  the  "corona"  is  that  given  in  the  *  Japan  Gazette,'  September  21st,  in  which 
it  is  stated  that  shortly  after  noon  on  August  30th  "  the  sun  seemed  to  diminish 
in  power,  and  a  uniform  yellowish-grey  haze,  gradually  deepening  in  intensity, 
spread  over  the  sky,  and  at  two  hours  before  sunset  the  sun's  rays  were  blended 
into  a  faint  halo  emerging  from  a  globe  of  light  no  larger  than  the  full  moon." 

A  similar,  though  less  definite,  observation  is  that  of  M.  Mareuse,  at  Guay- 
aquil, who  reports*  that  the  sun  on  September  lst-5th  was  surrounded  by  a  light 
atmospheric  film  of  a  coppery  hue,  through  which  the  sun  could  scarcely  shed  its 
light ;  it  appeared  like  silver  set  in  gold. 

The  first  detailed  observation  of  it  was,  however,  made  by  Mr,  Bishop  at 
Honolulu,  on  September  5th,  simultaneously  vdth  that  of  the  twilight  glows  and 
cloud-haze,  which  first  reached  that  place  on  this  date. 

It  is  important  to  notice  his  description  of  it,  since  we  are  thus  enabled  to 
establish  its  identity  with  the  phenomena  witnessed  in  Europe,  America,  and  other 
regions,  more  than  two  months  subsequently.     He  says  (^) : — 

"  Permit  me  to  call  special  attention  to  the  very  pecuUar  corona  or  halo  extending 
from  20°  to  30°  from  the  sun,  which  has  been  visible  every  day  vnth  us,  and  all  day,  of 
whitish  haze  vdth  pinkish  tint,  shading  off  into  lilac  or  purple  against  the  blue.  I 
have  seen  no  notice  of  this  corona  observed  elsewhere.  It  is  hardly  a  conspicuous  object." 

Since  this  event  it  has  generally  been  known  as  "  Bishop's  Ring,"  in  honour  of 
its  first  discoverer. 

Next  we  have  an  observation  on  September  8th,  on  board  the  Sbotia,  in 
10°  N.  and  53°  E.,  of  a  "partial  halo  forming  at  times  round  the  sun." 

The  Thesmlus,  on  September  16th,  in  28°  29'  S.  and  81°  45'  K,  reports  "a 
red  haze  round  the  moon  all  night." 

On  September  15th,  the  Carola,  in  14°-8  N.,  20°-8  W.,  mentions  "a  halo  as 

*  *  L'Astronomio/  Flammabion. 


ON  THE  LAEGE  CORONA  nOlTSB  THE  SUN  AND  MOON.  233 

visible  round  the  moon,  having  a  deep  red  outer  margin"  (^)  This  observation  on 
board  the  Carola  is  very  important  in  showing  that  the  ring  round  the  sun  was  not 
the  ordinary  ice-crystal  refraction  halo,  in  which  the  red  band  is  innermost,  but  a  true 
diffraction  corona,  in  which  the  red  occurs  on  the  outside  border.  This  reddish  or 
coppery  border  was  frequently  observed  without  its  ring-character  being  specially 
noted.  Thus,  on  September  16th,  Mr.  Maxwell  Hall,  in  Jamaica,  observed  "an 
unusual  copper  colour  in  the  sky  near  the  sun,  which  was  afterwards  very  strongly 
marked."*  On  September  15th,  the  Superb,  in  10°  N.,  146°  W.,  noticed  a  "halo  "  (?) 
45*  in  diameter. 

On  September  16th,  from  the  Coppename,  42°  0'  N.,  39°  29'  W.,  a  halo  was 
observed  round  the  moon  at  8  p.m.,  which  may  or  may  not  have  been  the  same 
phenomenon.  After  this,  we  have  some  observations  within  the  tropics  in  October, 
which  point  distinctly  to  the  same  corona  which  was  afterwards  observed  more  generally. 

Thus,  on  October  2nd,  the  Orissa,  in  18°  17'  N.,  86°  44'  E.,  notices  a  red  glare  or 
halo  roimd  the  sun,  from  25°  to  30°  in  diameter.  On  October  1 4th,  the  same  ship,  in 
11°  37'  N.,  82°  57'  E.,  observes,  from  8  p.m.  to  midnight,  "a  halo  or  circle  round 
the  moon  45°  in  diameter ; "  while  on  October  17th,  the  Glencaim,  in  13°  34'  S., 
91°  32'  E.,  notices  '^  a  very  broad  ring  round  the  moon  of  a  dark  reddish  colour ; " 
and,  in  addition  to  these,  we  have,  on  October  10  th,  Mr.  H.  Pabkeb's  observation  in 
Ceylon  of  a  limar  corona,  the  sun  being  normal  (i.e.,  the  green  tint  had  gone),  but 
dimmer  than  usual  at  sunrise  and  sunset,  and  on  October  1 8th,  at  Oakwood,  California, 
the  s\m  was  seen  encircled  by  a  white  ring  on  the  day  immediately  preceding  the 
first  appearance  of  the  twilight  glows  in  that  locality  ;  while  on  November  1st,  the 
Rev.  A.  W.  Hbyde  observed,  at  Kailong,  Lahoul  (Himalaya),  a  white  circular  sheen 
round  the  sun,  of  from  40°  to  80°  in  diameter. 

Thenceforward  we  have  frequent  evidence  of  the  appearance  of  the  corona  in 
Europe,  America,  Asia,  and  other  parts,  in  association  with  the  glows  and  other 
phenomena  in  November,  December,  and  January,  and  everywhere  of  substantially 
the  same  physical  aspect,  size,  and  order  of  colours. 

Regarding  the  order  of  the  colours,  while  there  seems  to  be  some  degree  of 
divergence  as  to  the  precise  quality  of  the  tints,  especially  of  the  interior  part, 
there  is  a  general  consensus  of  opinion  as  to  the  order  being  blue  or  white  on 
the  inside,  and  red  at  the  border,  or  the  reverse  of  that  in  the  ice-crystal 
halo. 

A  high  authority.  Dr.  Meldrum,  F.R.S.,  who  was  one  of  its  earlier  observera  in 
the  tropics,  spoke  of  it  at  the  October,  1883,  meeting  of  the  Mauritius  Meteorological 
Society,  as  "  a  whitish  silvery  patch  surrounded  by  a  brownish  fringe,  with  a  radius  of 
from  12°  to  24°,  according  to  the  position  of  the  sun." 

Other  observers  describe  it  as  follows  : — 

•  *  Jamaica  Weather  Report/  November,  1883. 


234 


MB.  E.  DOUGLAS  ABCHIBALD 


TABLE  I 


Date. 

Observer. 

Locality. 

Remarks. 

1883. 

C)  Not.  1 

Eev.  A.  W.  Heyde  • . 

Kailong,    Tiahoul, 

White   inside  and  red  outside; 

33°N.,77°B. 

never  seen  before. 

O  Nov.  26 

Miss  Annie  Ley 

Lutterworth 

White,  with  broad  halo  of  a  pale 

pink  colour. 
Whitish  light,  fringed  with  pale 

(»)  Nov,  (end  of)  and  Dec. 

Gapt.DeB.  Capello.. 

Lisbon 

(beginning). 

orange-rose;  region  not  cir- 
cuLu*. 

(•)  Nov.  27  and  Dec.  15  . 

T.  W.  Backhouse     . . 

Sunderland 

Pink  outside,  with  bluish  centre ; 
never  observed  previous  to 
Nov.  27,  though  a  constant  halo 
observer  for  26  years. 

C)  Nov.,  1883,  to  Feb., 

Hon.  Bollo  Russell . . 

Richmond.  • 

Inner  part  white,  outer  pale  red 

1884. 

• 

or  lilac. 

C)  During  the  same  time 

E.  D.  Archibald      . . 

Tunbridge  YiTells.. 

Inner  part  milk-white  and  outer 
reddish-brown. 

(•)  Nov.  30 

Herr  Wulst . . 

Dessau 

Silver  coloured,  with  brownish 
border. 

(")Deo.  1 

Dr.  von  Bezold 

Munich     . . 

W  hitish  in  centre,  with  brownish 
coloured  border. 

(")Deo.  12 

Professor  Divers     • . 

Tokio 

Silvery  glare,  bordered  by  a  dasty 
reddish-brown  or  purplish  ring. 

1884. 

(»)Jan.  2 

Herr  Metzger 

Flensburg . . 

A  bright  blue  spot  with  a  reddish 
border. 

(")  Dec.  and  Jan. 

Dr.  Galle      .. 

Breslau     •  • 

The  periphery  was  weak,  brownish 
pale  red,  and  inside   a  white 

gleam ;    inner    diameter    20*^, 

outer  diameter  40°. 

COFeb.  8 

Professor  Le  Conte .  • 

Calif  omia . . 

Whitish  glare  of  20°  to  25=^ 
radius. 

(«)  From  Nov.,  1883,  to 

M.  ThoUon    . . 

Nice 

Glowing  white,  very  slightly  tinted 

July,  1884. 

with  red  outside  and  blue  inside. 

(")  May  19,  1884 

Prof.  Ricc5  . . 

Palermo    . . 

Outer  rim  violet. 

(")  Deo.,  1883,  to  May, 

1884. 
(")  Sept.  22, 1884       •. 

Dr.  Assmann 

Magdeburg 

Outer  rim  brown-violet. 

Prof.  A.  Comu 

Paris 

Order  of   tints  of    corona  from 

within  outwards,  blue,  neutral 

grey,  brown-yellow,  coppery- 
red,  purple-red,  dull  violet. 

The  preceding  descriptions,  which  by  no  means  exhaust  the  entire  category,  but 
which  we  have  casually  selected  to  exhibit  their  general  similarity,  and  the  universal 
character  of  the  phenomenon,  show  that  the  sun  was  surrounded  by  a  white  space 
bordered  by  a  (circular  or  elliptical)  reddish  rim ;  and  though  there  are  considerable 
differences  in  the  description  of  the  precise  tint  of  both  the  interior  and  the  border, 
the  substantial  identity  of  the  phenomenon  in  different  parts  of  the  world  cannot  be 
questioned. 

Persons  differ  much  in  their  estimates  of  colour,  and  when  one  speaks  of  the 
interior  as  blue  and  another  as  white,  we  are  inclined  to  suspect  that  the  colour  in 


ON  THE  LAEGE  CORONA  ROUND  THE  SUN  AND  MOON. 


285 


the  first  case  may  have  been  partly  due  to  contrast  with  the  border,  which  would 
naturally  first  attract  attention,  and  also  be  more  likely  to  retain  it,  than  the 
intensely  brilliant  inner  space.  It  is  probable,  however,  that  in  the  present  case  the 
bluish  tint  spoken  of  in  some  cases  (though  the  majority  make  it  white  or  silvery), 
may  really  have  had  an  objective  presence,  and  that  the  order  from  within  outwards 
was  more  that  which  was  minutely  described  by  Prof.  Cobnu,  viz. :  blue,  neutral  grey, 
brown-yellow,  coppery-red,  purple-red,  dull  violet — analogous  to  the  order  of  the 
spectrum  colours,  only  flatter  in  tone. 

The  average  size  of  this  coronal  appendage  may  approximately  be  gathered  from 
an  examination  of  the  different  angular  measurements  (some  evidently  rather  rough 
guesses)  of  its  radius  or  its  diameter  by  different  observers. 

The  following  list  gives  nearly  all  we  have  been  able  to  collect,  including  one 
or  two  roimd  the  moon  : — 

TABLE  11. 


the  Sun. 

Date. 

Observers. 

Locality. 

1883. 

C) 

40°  [to  60°] 

From  September 

5,  onwards   . . 

Bev.  S.  E.  Bishop   .  • 
Rev.  A.  W.  Heyde  . . 

Honolulu. 

C) 

40°  to  80°  (?) 

November  1      . . 

Lahoul. 

(») 

50° 

Noyember  25   . . 

J.E.Clark   .. 

York. 

n 

44° 

NoTember  25    . . 

Miss  Annie  Ley 

Lutterworth. 

(») 

40°  to  46° 

December  5      . . 

1884. 

E.  Marchund 

St.  Genis. 

{^ 

50° 

January  13 

W.  G.  Brown 

Virginia. 

40°  to  44° 

•  • 

Dr.  Kiessling 

pnner. 
(«)       L2O'' 

oater.T 
33°.  J 

•  • 

Dr.  Ejremser, . 

Schneekopi)e.* 

(") 

40°  to  50 

Jannary  24 

Prof.  Divers . . 

Tokio. 

(-) 

40°  to  60 

February  8       •  • 

Prof.  Le  Conte 

California. 

(»)            20° 

40° 

March  24 

B.  W.  S 

44°  to  46° 

April     •  • 

B.  Douglas  Archibald 

Tunbridge  Wells. 

umer. 
(»)     21°  36' 

max.  intensitj.     outer. 
30°  20-          42°  52' 

May  19 . . 

Prof.  Ricc6  •  • 

Palermo. 

inner. 

outer. 

(»)            24° 

40°  to  44° 

May  and  June    * 

Dr.  Assmann 

Magdeburg. 

n 

48° 
middle  of         outer 

July  23  • . 

D.  A.  Arcimis 

Madrid. 

inner. 

red.             margin. 

(")   14°  to  20° 

24°  to  28°     36°  to  44° 

Summer 

F.  A.  Forel   . . 

Switzerland. 

n         23° 

•• 

Dr.  von  Bezold 

Munich. 

*  'Inserted  here  after  the  means  had  been  taken.     In  computing  the  means,  the  extreme  value  is 
the  outer  diameter,  and  the  average  or  single  value  for  the  inner. 


236 


MB.  E.  DOUGLAS  ABGHIBALD 


Table  II. — (continued.) 


Angpalar  Diameter  of  Corona  round 
the  Moon. 

Date. 

Observers. 

Locality. 

interior.                      exterior. 
C)            15° 

r)      -               -ts" 

C)                           30° 
(«)                           36° 

1883. 
September  16  . . 

Ootolier  14       . . 

1884. 
January  4 
January  4 

S.  Oarola      .. 
S.OrisM 

Prof.  Hasen . . 
Dr.  Eremser 

fl4"48'N. 
120°48' W. 
f  11°  37'  N. 
182°  67' E. 

U.S. 
Sobneekoppe. 

K  we  take  the  averages,  excluding  the  doubtfully  large  value  found  by 
Rev.  A.  W.  Heyde,  at  Lahoul,  and  Dr.  Kbemser's,  we  find  the  following  values  for 
the  corona  round  the  sun  : — 


Inner  diameter. 

2r  r 


Outer  diameter. 
45^  33' 


These  averages  accord  very  fairly  with  those  of  Professors  R1006,  Assmann, 
and  FoEEL,  which  appear  to  have  been  the  most  carefully  measured  of  the  entire 
series. 

We  shall,  therefore,  aa  a  probable  average,  take  the  inner  white  portion  to  be 
21^,  and  the  entire  ring  up  to  the  outer  red  to  be  45°  30'  in  diameter.  The  diameter 
of  the  Ixmar  ring  appears  to  have  been  generally  smaller,  judging  from  the  few 
observations,  and  this  seems  to  be  natxuul  in  consequence  of  its  inferior  brilliancy, 
which  would  tend  to  render  the  extreme  red  border  invisible.  From  the  obser- 
vations in  the  Table,  there  does  not  seem  to  have  been,  and  indeed  from  such 
a  comparatively  limited  series  of  observations  it  would  be  difficult  to  infer  that  there 
was,  any  sensible  alteration  in  the  size  of  the  "  corona"  during  the  first  twelve  months 
of  its  appearance. 

Since  the  preceding  paragraphs  were  written,  a  pamphlet  entitled  'Beobach- 
tungen  tiber  die  Dammerung  und  seine  Beziehungen  zum  Bishop'schen  Sonnenring,' 
by  Dr.  Albert  Riqqenbaoh  of  Basle  (1886),  has  appeared,  in  which  the  author  gives 
some  later  observations  of  the  diameter  of  the  corona  (Bishop's  Ring),  when  the  sun 
was  at  a  high  altitude,  and  a  further  list  during  1885  of  its  dimensions  at  sunrise 
and  sunset. 

From  the  first  list  we  extract  the  following :-— 


ON  THE  LABGE  CORONA  ROUND  THE  SUN  AND  MOON, 


237 


Year.       Month 

Diameter  of  Ring. 

Observer. 

Source. 

Inner. 

Middle. 

Outer. 

1884r-ATig.  7    .. 
Aug.  22, 23 

1886— Jan.  3-5  . . 
May  9     .. 
Jtdj  3     . . 

20° 
14°  to  20° 

22° 

30° 

■      12° 

26°  to  34° 
24°  to  30° 

26° 

48° 
36°  to  44° 

32°  to  34° 

50° 
36°  to  40° 

Flogel       . . 
Forel 

Kremser    .. 
Bnsch 

Biggenbach,  in  the 
Engadine. 

'  Das  Wetter,'  Bd.  i.,  p.  221. 
'Archives  de  Geneve,'  xii., 

p.  175. 
'Met.  Zeit8.,'Bd.ii.,  p.  142. 
'DasWetter.'Bd-ii,  p.  116. 

Means 

20°  12' 

27°  40' 

41°  48' 

The  means  from  these  observations  do  not  sensibly  differ  from  those  derived  from 
our  former  list,  though  there  appears  to  be  a  slight  falling  off  in  the  size  of  the  inner 
and  outer  diameters.  The  individual  observations,  however,  differ  so  much  inter  se, 
that  no  importance  can  be  attached  to  this  circumstance.  The  means  from  the  entire 
series  of  twelve  high-sun  observations,  from  November,  1883,  onwards,  given  by 
Biggenbach,  are  as  follows,  with  our  former  ones  for  comparison  : — 


Diameter  of  Corona. 

Ri^enbach. 

Former  List. 

Inner , 

Middle  of  the  red 

Outer 

20° 
28° 

44° 

21°  7' 

28°  10'  (2  obs.) 

45°  33' 

The  values  will  be  seen  to  be  very  fairly  accordant,  especially  when  it  is  remem- 
bered that  they  were  measured  for  the  most  part  by  different  observers.  The  second 
Table  gives  the  diametera  of  the  corona  at  sunset  from  sixty-three  observations  taken 
at  different  dates  in  1885,  and  arranged  for  different  solar  zenith  distances,  in  order 
to  exhibit  the  dilatation  of  the  ring  with  increasing  solar  depression.  The  means  are 
as  follows  : — 


Zenith  Distance  of  Sun's 

Diameter  ♦  of 

Centre. 

Inner  bright 
space. 

Brightest  part 
of  red. 

Outer  limit  of 
red. 

60°     to  78° 
81°-6  to  88°-9 
89°-l  to  92°-3 

12° 

27°-8 
35° 

26° 
32°-4 

38°-4 

32°-8 

49°-2 

*  Converted  from  radius  as  originally  given. 
2l 


MR.   E.   DOUGLAS  ARCHIBALD 

Dr.  RiGGENBACH  then  gives  a  list  of  the  angular  distances  of  the  brightest 
portions  of  the  purple  sunset  glow  from  the  sun,  at  different  zenith  distances  of  the 
latter,  in  order  to  show  the  close  connection  of  the  shape  and  extent  of  the  glow  with 
those  of  the  corona.  The  mean  of  thirteen  observations  of  this  portion  of  the  glow, 
gives  it  a  radius  from  the  suns  centre  of  18°* 6,  or  a  diameter  of  37^*2,  the  sun's 
zenith  distance  varying  from  92°'l  to  93°'8. 

The  brightest  part  of  the  purple  glow,  in  fact,  commences  about  the  middle  or 
brightest  part  of  the  corona  when  this  has  reached  its  greatest  dilatation. 

A  few  single  observations  of  the  corona  and  the  purple  glow  are  placed  together 
for  direct  comparison : — 


1885 

Solar  distance  of  the  brighteet  part. 

Corona. 

Purple  glow. 

September  15 
II          16 

17        ..        .. 

1)                       A«5                  •  •                     •  ■ 

18"-6 
17°-8 
18°-7 

21°-2 
16°1 
17-2 
18°7 

The  relationship  between  these  two  phenomena  will  be  considered  further  on. 

Diurnal  and  Secular  Duration  of  the  large  Corona. 

The  corona  round  the  sun  appears  to  have  continued  everywhere  with  little 
change  in  its  character,  and  only  a  gradual  decrease  in  its  brilliancy,  from  the  date  on 
which  it  was  first  observed  up  to  the  spring  of  1886,  and  although  not  observed  (or 
perhaps  noticed)  so  soon  as  the  twilight  glows,  it  was  subsequently  seen  wherever 
these  occurred,  and  in  proportion  as  their  brilliancy  waned  it  came  more  and  more 
into  popular  notice.  It  i^  possible,  indeed,  that  near  the  Equator,  where  the  matter 
causing  the  appearances  seems  to  have  been  densest,  the  corona  may  have  been  some- 
what modified,  so  as  to  appear  merely  in  the  form  of  a  glare  (such  as  was  noticed  by 
the  brig  Hazard  and  other  ships,  to  surround  the  sun),  and  without  the  red  border 
which  was  generally  observed  beyond  the  tropics. 

It  may  also  possibly  have  been  this  fact  which  caused  the  remarkable  absence  of 
notice  of  the  corona  all  over  the  northern  parts  of  South  America  and  at  other 
equatorial  places,  when  the  blue  and  green  appearance  of  the  sun  was  attracting 
public  attention,  and  that,  as  Mr.  Bishop  remarks  concerning  the  twilight  glows, 
which  were  more  noticeable  at  Honolulu  than  at  Fanning  Island,  the  corona  came 


*  Radios  of  the  inner  limit  of  tlie  red. 


ON  THE  LARGE  CORONA  ROUND  THE  SUN  AND  MOON. 


S3& 


out  in  its  best  colours  only  where  the  matter  waa  less  dense,  and  therefore,  probably, 
more  homogeneous. 

The  following  remarks  regarding  its  secular  duration  at  different  places  will  show 
something  of  the  nature  of  its  persistence,  and  we  have  further  evidence  that  in  most 
places  where  it  was  noticed,  either  simultaneously  with,  or  shortly  subsequent  to,  the 
glows,  it  has  continued  to  be  seen  whenever  the  conditions  were  favourable,  such  as  a 
clear  atmosphere,  or  a  cloud  which  hid  the  sun's  direct  rays. 


TABLE  IIL 


Period  of  Continuance. 


Observer  or  Authority. 


Locality. 


1883. 
(^)  All  through  September    . . 
(*)  September  6  to  December  15,  1883 
C^)  November,  1883,  to  April  3,  1884 
(*)  November  11  to  21 
(*)  November,  onwards 
(*°)  Several    weeks    previous  to   De^ 
cember  24 


(")  December  to  February,  1884 

188i. 
(*»)  February  20  to  March  24  . . 

n  April       ..     /;■     .. 


n 
n 
n 


(^)  Beginning  of  March  to   end    of 
April 
May  14,  and  for  weeks  back 
June  and  July 

May  18  to  September  6   (inter- 
mittently) 
(«)  July  29  to  August  3 
(*•)  July  22  to  August  4 
C"*)  November,  1883, toNovember,  1884 


Brig  Hazard     , . 
Rev.  S.  E.  Bishop 
T.  W.  Backhouse 
Dr.  Neumayer . . 
Maxwell  Hall  . . 


F.  Perrin 

Hon.  F.  A.  Rollo  Russell 

Dr.  G.  F.  Burder 
Rev.  S.  E.  Bishop 


Dr.  Kiessling 
C.  L.  Prince 
C.  L.  Wragge 


J.  Gledhill 
W.N.Hartley.. 
Prof.  F.  A.  Forel 
Rev.  A.  W.  Heyde 


Pacific,  from  New  Hanover  to  Honolulu. 

All  through  the  Hawaiian  Archipelago. 

Sunderland. 

Switzerland. 

Jamaica. 


Mont  Fetoules.       (The 

bad  been  seen.) 
Richmond,  Surrey. 


guides    said 


Clifton,  Oloacestershire. 
Honolulu.*      (Seen   constantly   since 
September  5,  1883.) 

Hamburg. 

Crowborough,  Sussex. 
Adelaide. 

Halifax,  Yorkshire. 

Switzerland. 

Merges. 

Lahoul,  Himalaya. 


And  thence  Professor  Forel  carries  on  the  observations  almost  up  to  date 
(October,  1886)  in  the  following  list,  which  he  has  forwarded  to  the  Committee, 
and  which  ^ves  all  the  dates  on  which  he  has  seen  the  corona  since  the  summer 
of  1884:— 


♦  Another  observer,  Mr.  C.  J.  Lyons,  carries  it  on  to  May  29, 1884,  at  the  same  place. 


2  I  2 


240 


MB.  E.  DOUGLAS  ARCHIBALD 


Year. 

Month. 

Dates. 

July 

22,  23,  25,  26,  28,  29,  30,  3i 

August 

i,  2,  3,  4,  /«.  /»,  20,  22,  23,  24,  25,  27,  30,  31 

1884        ..< 

September 

1,  2,  4,  5,  6,  7.  8, 12, 14, 15, 16, 17, 18 

October     . . 

26,  27,  28,  29,  30, 31 

November.. 

3,  4,  8, 18, 19,  20,  23,  24,  27,  30 

« 

December  . . 

2,  4,  7,  9,  11,  13, 15,  18 

Jannaiy     . . 

4,  5,  8, 12,  13,  27,  29,  31 

Febmary  .. 

1,  4,  6,  7,  8, 10, 12,  23,  24,  26,  27 

March       .. 

7,  8,  9, 14, 15, 17, 19,  23,  31 

April 

I,  7,  8, 14,  15,  22,  24,  27,  28 

May 

5,  7,  8,  9,  /0, 16, 17, 18, 19,  21,  23,  24,  25,  28,  29, 

3 

1886 

June 
July 

5,  7, 14, 15, 19,  21,  23,  25,  28 
1,  4,  10, 13, 19,  21,  27 

Aagast 

2,  4,  6,  7,  8,  9,  10,  //,  13, 15,  22 

September 

4,  5,  6, 10,  i3,  i4, 15, 18,  24 

October     . . 

2,  4,  7,  9, 15,  16,  22,  27,  30 

November. . 

1.  2,  3,  27 

December . . 

1,  2,  9,  29 

January     . . 

30(?) 

Februaiy  . .         , . 

i9 

March        . . 

14,30 

1886 

April 
M^y 

2, 10(?)  29(?) 
7 

June          . .         . . 

3 

July 

•  • 

August     .. 

..• 

Note. — The  figures  in  italics  represent  observations  taken  during  ascents  above  1,000  metres ;  tbe 
rest  were  taken  in  Swiss  valleys  at  400  metres  above  sea  level. 


The  letter  is  dated  December  4th,  1886,  and  Professor  Forel  makes  the  follow- 
ing remarks : — 

"While  up  to  October,  1885,  I  have  noticed  the  appearance  of  the  ring  on  the 
average  ten  times  per  mensem;  in  November  and  December,  1885,  I  have  seen  it  only- 
four  times  per  mensem.  In  the  first  months  of  1886  I  have  only  nine  observations,  of 
which  three  were  doubtful,  and  two  were  taken  in  ascents  of  mountains. 

"Lastly,  since  July,  1886, 1  have  no  longer  observed  the  phenomenon.  Moreover, 
though  I  have  been  in  conditions  favourable  for  observation,  and  have  resided  during 
July  and  August,  1886,  in  the  Alps  of  the  Valais,  at  an  elevation  of  over  6,000  feet, 
and  have  sometimes  attained  the  altitude  of  9,000  feet,  I  have  not  observed  the 
slightest  indication  of  "  Bishop's  Ring."  My  friends,  who  permanently  reside  between 
9,000  and  12,000  feet  above  sea-level,  have  informed  me  of  the  complete  disappearance 
of  the  coloured  circle.      The  sole  observations  which  I  have  received  during  the  last 

•  In  a  recent  letter  to  *  Nature,'  vol.  xxxv.,  p.  601,  Professor  Stonb  mentions  the  corona  as  invisible 
during  the  summer  months  of  1886,  but  visible  again  on  October  15,  since  which  date  it  has  not  been 
seen. 


ON  THE  LARGE  CORONA  ROUND  THE  SUN  AND  MOON. 


241 


six  months  are  (1)  that  of  July  the  19th,  1886,  duriog  the  ascent  of  Mount 
Pleureur,  3,706  metres  (12,159  feet),  by  MM.  Kundig  and  Ischam,  of  Geneva;  and 
(2)  that  of  July  the  26th,  1886,  on  the  Col  d'Herens,  3,460  metres  (11,352  feet), 
by  Mr.  CouN  Campbell,  of  Dundee." 

Professor  Forel  concludes  as  follows  : — 

"Bishop's  Ring  has  appeared  continuously  in  our  country  from  November,  1883, 
up  to  October,  1885.  From  November,  1885,  to  July,  IS 86,  it  has  been  observed 
discontinuously.     At  the  end  of  1886  it  has  become  no  longer  visible." 

Professor  Ricc6,  of  Palermo,  has  also  forwarded  a  list  of  observations,  which, 
though  it  does  not  embrace  so  long  a  period,  is  interesting,  as  showing  that  the 
phenomenon  w;as  a  universal  one,  and  that  the  gaps  in  Professor  Forel's  series  were 
chiefly  due  to  local  conditions,  such  as  unfavourable  weather,  &c.  Thus,  the  ring 
was  observed  on  the  following  dat^s  :^ 


Year. 

Month. 

Dates. 

1886      ... 

April 
May 
Jnne 
Jnly 

1,  2,  3,  4,  6,  6,  7,  8,  9, 10,  11, 12, 13, 17,  20,  26,  27,  29 

1,  2,  3, 5,  6,  7,  12, 13,  26,  27 

2,  3,  6,  6, 11,  12,  20,  21,  22,  26,  27,  28 
6,21 

If  these  dates  be  compared  with  those  of  Professor  Forel  it  will  be  found  that 
only  ten  coincide. 

Professor  Ricc6  has  also  furnished  a  table  of  the  intensity  of  the  phenomena 
from  its  commencement,  measured  by  an  arbitrary  scale  of  0 — 10.  On  taking 
monthly  averages  of  these,  where  there  are  enough  observations,  we  get  the  following 
results : — 

Mean  Intensity  of  Corona. 

1883.— December,  6-5. 

1884.— January,  8*0;  February,  8'0;  March,  8*4;  April,  8'6(max.);  May,  5*1  ; 
June,  6'0;  July,  6*3;  August,  7*5;  September,  6*8;  October,  7*5;  November,  8 '4. 

1885.— April,  2-9  ;  May,  2*0  ;  June,  V7  (min.). 

• 

In  examining  the  results  of  this  latter  table  we  must  remember  that  the  figures 
are  not  all  intercomparable,  owing  to  the  observations  having  been  made  in  different 
localities.  Thus,  up  to  May,  1884,  they  were  made  at  Palermo  ;  in  June,  at  different 
places  while  travelling  from  Turin  to  Modena;  from  July  to  the  end  of  1884,  at 
Castelvetro,  south  of  Modena ;  and  in  1885,  again  at  Palermo, 

Taking,  then,  the  first  six  and  the  last  three  months,  we  find  a  gradual  rise 
up  to  a  maximum  about  April,  1884  ;  and  since  then  evidence  of  a  gradual  decline 
down  to  June,  1885. 


242  MR.  E.  DOUGLAS  ARCHIBALD 

This  agrees  with  other  casual  evidence  in  making  the  maximum  of  the 
corona  in  Europe  in  the  spring  of  1884,  and  about  three  or  four  months  after 
the  maximum  of  the  twilight  glows  in  the  same  latitudes.  Taking  all  the  facta 
together  regarding  secular  duration,  we  find  that  while  the  twilight  glows 
ceased  to  attract  attention  after  February,  1884,  the  corona  survived  them  with 
remarkable  persistence,  and  that  even  up  to  the  spring  of  1886,  or  nearly  three 
years  from  the  time  at  which  it  first  appeared,  it  still  remained  a  conspicuous 
phenomenon. 

Its  diurnal  duration  in  favourable  circumstances  seems  to  have  been  continuous. 
Thus,  Mr.  Bishop  speaks  of  it  as  being  **  visible  every  day  and  all  day,"  (^)  and  Mr. 
T.  R.  Clapham,  of  Lancaster,  remarks  that  the  corona  can  be  seen  any  day  at 
mid-day  when  the  sky  is  clear. 

Dr.  Meldrum  (^^)  notices  that  the  corona  is  visible  "  during  the  greater  part 
of  the  day;"  and  others,  such  as  Professor  Le  C!onte  (California),  M.  Thollon, 
C.  L.  Prince,  T.  W.  Backhouse,  Dr.  Assmann  (Magdebiu-g),  Professor  F.  A.  Forel 
(Merges),  C.  L.  Wragge  (Adelaide),  and  the  writer,  show  by  their  statements  that 
this  was  the  case  all  over  the  world.  It  was  best  seen  when  the  lower  air  was  free 
from  dust,  as,  for  instance,  after  rain,  and  especially  when  a  dark  cloud  hid  the  sun 
and  allowed  the  red  rim  to  be  seen  round  its  border.  In  such  circumstances,  as 
Professor  Forel  substantially  remarked,  the  lower  strata  of  the  atmosphere  are  in 
a  shadow,  and,  therefore,  the  white  light,  which  they  usually  disperse,  no  longer 
obliterates  the  delicate  tints  of  the  corona.  (^^) 

One  point  deserves  to  be  noticed  in  connection  with  the  secular  duration  of  the 
corona,  viz.,  that  while  in  November  there  was  apparently  a  great  decline  in  the 
brilUancy  of  the  twilight  glows  at  Honolulu,  Mr.  Bishop  observed  that  the  corona 
continued  unaltered.  (^^)  The  same  fact  was  observed  during  the  temporary  abate- 
ments of  the  glow  phenomena  in  Europe,  showing  evidently  that  the  physical  cause 
which  produced  the  corona  was  independent  of  certain  circumstances  which  regulated 
the  development  of  the  glows  at  sunrise  and  sunset.  Since  the  glows  have  disap- 
peared, the  survival  of  the  corona  lends  additional  support  and  importance  to  this 
conclusion. 

The  general  constancy  of  the  corona  under  various  meteorological  conditions, 
both  secular  and  diurnal,  accords  with  the  evidence  aflforded  elsewhere  of  the 
elevation  of  the  stratum  in  which  it  was  generated,  far  above  ordinary  atmospheric 
disturbances,  though  probably  not  above  upper  aerial  currents  of  a  continuous  and 
general  character. 

Peculiar  Features  of  the  Corona. 

It  remains  for  us  to  notice  certain  peculiar  features  which  were  exhibited  by  the 
large  corona  after  it  fii'st  became  visible  in  Europe,  in  November,  1883  ;  and  also  to 


ON  THE  LARGE  CORONA  ROUND  THE   SUN  AND  MOON.  243 

point  out  those  ia  which  it  appears  to  differ  from  all  ordinary  phenomena  of  a  similar 
nature. 

(1.)  It  was  noticed  that  while  the  corona,  during  midday,  and  when  the  sun  was 
at  a  high  altitude,  was  nearly  circular,  as  the  latter  declined  towards  the  horizon  the 
corona  lengthened  out,  and  the  sun,  instead  of  occupjring  the  centre  of  the  ring, 
hecame  excentric  to  it,  towards  its  lower  boundary.  This  was  noticed  specially  by 
W.  G.  Brown,  of  Virginia ;  (*')  Prof.  A.  Kicc6,  of  Palermo ;  0«)  Dr.  Kiessling  ;  («*) 
T.  W.  Backhouse,  of  Sunderland ;  Prof  Coenu,  and  Dr.  Meldrum.  {^^)  Dr. 
Bjoessung  explains  this  excentricity  as  follows  : — 

"  At  sunset  the  sun  has  constantly  become  excentric  near  the  lower  border  of 
the  central  area  [a  diffraction  field],  so  that  when  the  sun  has  been  at  about  10° 
altitude  a  strikingly  bright  glowing  blue  spot  has  appeared  about  23°  to  22°  above  the 
horizon  from  which,  when  the  sun  has  sunk  lower,  the  first  purple  glow  has  been 
suddenly  developed.  These  observations  clearly  show  that  the  problematic  purple 
glow  is  simply  the  upper  portion  of  a  very  excentric  diffraction  image,  such  as  can 
be  experimentally  formed  by  allowing  the  edge  of  the  cloud  molecules  to  act  on  a 
vertical  plate  of  glass,  the  size  of  which  molecules  rapidly  increase  from  above  down- 
wards." 

This,  however,  does  not  tally  with  the  fact  noticed,  amongst  others  by  M.  Cornu, 
that  the  lower  part  of  the  diffraction  ring  widens  out  as  the  sun  approaches  the 
horizon  ;  whereas,  if  the  above  cause  were  alone  in  operation  it  should  become 
narrower  and  more  curved  at  its  lower  edge. 

Prof.  Cornu  says  (^®) : — 

*'  The  concentric  reddish  corona  is  the  simplest  form  of  the  phenomenon.  It 
appears  in  this  geometrical  form  only  when  the  sun  is  at  great  altitudes  in  the  midst 
of  a  sky  sufficiently  clear ;  but  when  the  sun  is  lower,  the  lower  arch  of  the  corona 
widens  and  becomes  more  intense.  Below  this,  on  the  horizon,  arises  a  band  of  the 
same  colour,  which  also  widens  towards  the  corona  as  if  attracted  thereby.  This  band 
gradually  spreads  in  every  direction,  reaches  the  corona,  and  resolves  itself  into  a 
sort  of  globe.  During  this  metamorphosis  the  brilliant  inner  space,  of  a  slightly 
bluish-white,  remains  sensibly  circular,  but,  by  an  easily  explained  illusion,  the  sun 
seems  to  be  excentric  towards  the  lower  side." 

It  seems  to  us  that  this  latter  is  the  more  probable  interpretation  of  the  two ; 
though,  in  favour  of  the  former  acting  to  some  extent,  we  have  the  d  pi^iori 
probability  that  dust  would  tend  to  arrange  itself  in  the  order  of  the  sizes  of 
its  component  particles,  increasing  from  above  downw^ards. 

Dr.  Zenker,  in  an  article  on  the  corona,*  has  mathematically  exhibited  the 
eUipticity  of  the  corona  as  the  solar  altitude  decreases  as  follows  : — 

Let  ^  =  the  angular  altitude  of  the  sun  above  the  horizon. 
*  '  Met.  Zeitsch;  (1885),  vol.  ii.,  p.  400. 


244  MR.  E.   DOUGLAS  ARCHIBALD 

2  p  =  the  vertical  angle  of  the  cone  made  by  joining  the  exterior  rim  of  the 
corona  to  the  eye. 
a,  6,  the  major  and  minor  axes  of  the  section  made  by  this  cone  on  the  dust 

stratum  when  the  sun  is  not  in  the  zenith. 
Then  we  have 

a  COB  p 

h         s/  Bin  (^  -h  p)  sin  (^— p)  * 

When  the  sun  is  at  the  zenith,  <}>  =  90°  and  a  =  h,  and  the  ring  is  circular. 
When  the  sun  is  on  the  horizon,  <f>  =  p  and  ^  =  oo ,  and  the  curve  becomes  a 

parabola.      Finally,  when  <^  is    <  p,  j   becomes    negative,    and  the   curve  is   an 

hyperbola. 

Dr.  A.  KiGGENBACH,  in  his  pamphlet  already  referred  to,  thus  explains  the 
widening  of  the  corona  as  the  sun  approaches  the  horizon  *  : — 

"  The  widening  of  Bishop's  Ring,  which  begins  about  half  an  hour  before  sunset, 
and  reaches  its  maximum  soon  after  sunset,  arises  solely  from  the  reddening  of  the 
sun's  light  by  its  absorption  in  consequence  of  its  longer  path  through  the  lower 
atmospheric  strata ;  and  is  to  be  conceived  as  a  transmutation  of  the  diflfraction 
image  from  a  white  source  of  illumination  into  that  from  a  monochromatic  red.  At 
the  same  distance  from  the  sun  where,  shortly  before  the  disappearance  of  the 
ring,  the  maximum  brightness  of  the  red  lies,  the  purple  glow  first  makes  its 
appearance." 

From  this  and  the  preceding  extracts,  it  is  evident  that  considerable  diversity 
of  opinion  prevails  as  to  the  cause  or  causes  of  this  particular  phase  of  the  phe- 
nomenon. 

(2.)  Another  feature  of  the  corona  was  its  variation  when  seen  at  different  altitudes 
above  the  surface  of  the  earth.  This  has  been  noticed  both  by  Mr.  T.  W.  Back- 
house, of  Sunderland,  and  by  Professor  Forel,  of  Merges.  Both  observers  concur  in 
finding  the  corona  more  brilliant  when  seen  through  a  clearer  atmosphere,  such  as 
exists  at  lofty  altitudes.  The  former  describes  the  phenomenon  as  being  far  more 
striking  on  the  summit  of  the  Gomer  Grat,  10,289  feet  above  sea  level,  than  down 
below,  and  even  at  a  height  of  4000  feet  it  was  more  definite  than  at  sea  level.  (^') 
Professor  Forel  says  C^) : — "  I  verified  the  influence  of  altitude  on  the  corona. 
Starting  from  the  hospice  of  the  Grimsel,  1870  metres  (6135  feet),  where  the  red  circle 
was  well  defined,  I  saw  its  intensity  gradually  diminish  as  I  descended  into  the  valley 
of  Hasli;  at  Innertkirchet,  625  metres  (2051  feet),  the  red  was  imperceptible,  but  it 
reappeared  on  ascending  to  Rosenlaui ;  and  at  the  Grand  Schiedeck,  1960  metres  (6431 
feet),  the  corona  was  in  its  full  lustre.  I  never  saw  it  more  brilliant  than  when  on 
the  high  nSvls  of  the  F^e,  3000  metres  (9843  feet),  Kh6ne,  2800    metres  (9187 

*  '  Beobacbtungen  iiber  die  Dammernng,'  Ac.,  p.  16. 


y 


ON  THE  LARGE  CORONA  ROUND  THE  SUN  AND  MOON.        245 

feet)  or  Lower  Aar,  2550  metres  (8366  feet), glaciers,"  And  again: — "I  saw  the 
corona  in  the  Alps  of  the  Valais  and  Berne  from  August  18th  to  26th.  As  soon  as 
I  reached  1000  metres  (3281  feet)  the  phenomenon  reappeared ;  at  1500  metres 
(4921  feet)  it  was  very  distinct;  at  2000  metres  (6562  feet)  to  3000  metres 
(9843  feet)  its  hrilliancy  was  extraordinary." 

These  observations  are  important  as  showing  that  the  phenomenon  essentially 
belonged  to  the  upper  aerial  regions,  and  are  easily  explained  by  the  fact  that  the 
dustier  and  the  smokier  air  of  the  lower  strata  would  tend  to  overpower  by  their 
diffused  light  and  perhaps  also  to  absorb  the  delicate  mono-chromatic  tints  of  the 
corona  more  than  would  the  purer  and  more  translucent  air  of  the  upper  regions. 

Although,  as  we  have  before  remarked,  the  corona  was  observed  from  places  only 
slightly  elevated  above  sea  level  to  be  substantially  independent  of  weather  changes, 
it  was  noticed  to  be  more  brilliant  with  certain  phases  of  weather  than  others, 
especially  after  rain,  and  when  the  lower  strata  were  less  hazy  and  smoky  than  usual. 
In  fact,  the  smoke  of  large  cities,  such  as  London  and  Berlin,  seemed  to  render  it 
almost  invisible.  Such  vari^ttion,  however,  was  plainly  local  and  confined  to  the  lower 
atmosphere  alone. 

Certain  secular  changes  of  colour,  however,  independe^tly  of  those  due  to  the  state 
of  the  lower  atmosphere,  appear  to  have  been  noticed  by  a  few  persons,  amongst  whom 
was  Professor  G.  H.  Stone,  of  Colorado,  who,  in  a  paper  presented  to  the  Colorado 
Meteorological  Association,*  notices  that  the  corona,  or  "  sun-glow,"  as  he  terms  it, 
was  orange  in  November  and  December,  1883,  pink  or  reddish-brown  in  April,  1884, 
and  then  diminished  in  intensity,  becoming  slightly  orange  again  in  the  autumn  of 
the  same  year.     Since  then  it  had  become  dull  reddish-brown, 

**  It  was  least  intense  during  July  and  August  of  1884  and  1885,  It  was  most 
intense  during  November  and  December,  1883  and  1884." 

The  same  writer  notices  likewise  certain  variations  of  intensity  with  particular 
phases  of  weather,  the  inaximum  of  brilliancy  occurring  during  cold  weather,  and 
especially  before  a  cold  storm,  and  he  subsequently  endeavours  to  trace  a  causal  con- 
nection between  the  two  ;  but  as  the  sun-glow,  or  corona,  was  in  all  probability  formed 
in  the  same  haze  which  caused  the  glows,  and  which  evidently,  both  from  its  height 
and  behaviour,  had  very  little  connection  with  the  ordinary  currents  and  movements 
of  the  lower  atmosphere,  this  was  mainly  owing  to  the  lower  air  being  clearer  at  such 
times. 

In  support  of  this,  Mr.  Helm  Clayton,  writing  to  the  same  journal  in  June, 
1886,  says  : — "  Observations  bavebe^n  taken  for  several  months  on  the  visibility  of  the 
ring  and  of  distant  mountains  at  Blue  Hill  Observatory,  and  there  has  seemed  to  be  a 
close  parallelism  between  the  two  in  New  England.  The  ring  has  always  appeared 
brightest  when  the  mountains  were  clearest,  and  has  disappeared  when  the  mountains 

*  '  American  Meteorological  Journal,*  vol.  ii.,  No.  11,  March,  1886. 

2  K 


246  MK.   B.  DOUGLAS  ARCHIBALD 

disappeared  from  view."     Professor  Stone's  last  communication,  which  again  combats 
this  view,  is  appended  : — 

Disappearance  of  Bishop's  Ring  in  Colorado.* 

"  The  reddish  ring  about  the  STin  first  distinctly  appeared  here  (at  the  base  of  Pike's  Peak)  on 
Noyember  22nd,  1883.  For  several  dajs  before  that  date,  a  faint  discoloration  of  the  region  about 
the  sun  had  attracted  mj  attention.  This  gradually  grew  more  intense,  and,  on  the  day  mentioned, 
became  unmistakable.  The  subsequent  history  of  Bishop's  Ring  as  seen  at  this  place  is,  in  brief,  as 
follows  : — 

''  The  colour  was  most  intense  during  the  winter  of  1883-84,  and  diminished  in  brightness  from  that 
time  until  its  disappearance.  At  first  it  was  visible  almost  all  the  time.  Later,  it  appeared  only  at  the 
time  of  cold  storms,  which  were  accompanied  by  great  vertical  movement  of  the  air,  or  when,  for  any 
reason,  the  clouds  reached  to  a  great  height.  It  was,  on  the  average,  bright-er  during  the  winters  than 
in  the  snmmers ;  also,  it  was  brighter  when  the  sun  was  near  the  horizon.  Many  times  in  oold  weather 
there  has  been  not  a  trace  of  the  ring,  although  the  air  was  so  clear  that  peaks  a  hundred  miles  distant 
were  distinctly  visible  from  the  heights  behind  this  city.  At  other  times  the  ring  has  been  very  bright 
when  the  air  was  so  hazy  that  the  mountains  only  10  miles  away  were  hardly  visible.  During  the  later 
months  of  1885  it  was  invisible  most  of  the  time,  but  suddenly  flamed  ont  in  wonderful  intensity  at  the 
time  of  the  great  norther  of  January  9th-llth,  1886.  Then  for  about  two  months  it  frequently 
appeared  in  the  morning,  or  towards  evening.  During  the  warm  months  of  1886  it  was  not  seen.  On 
October  15th  it  appeared  distinctly.  About  a  week  later  it  appeared  very  faintly  a  few  times,  and 
since  then  I  have  not  been  able  to  see  a  trace  of  it.  My  observatious  have  been  made  at  elevations 
of  from  6000  to  about  18,000  feet,  and  there  was  bnt  little  apparent  dilEerence  in  intensity  at  the 
different  elevations.  It  is  well  known  that  the  atmosphere  here  is,  in  general,  very  dry  and  trans- 
parent. 

**  The  difFraction -ring  was  often  mora  coppery,  almost  rosy,  in  tint  at  the  time  of  the  northers,  and  in 
the  thickening  haze  in  the  upper  air  preparatory  to  hailstorms.  The  great  intensity  of  the  colour  at 
such  times,  and  its  peculiar  tint,  and  that,  too,  irrespective  of  the  amount  of  haze  in  the  lower 
atmosphere,  makes  it  probable  that  the  ring  was  in  part  due  to  difFraction  on  ice-particles.  If  so,  the 
ice-particles  may  themselves  have  been  due  to  precipitation  on  dust-particles.  The  fact  that  no  difFrac- 
tion-ring  has  been  seen  around  the  sun  during  the  past  winter  is  not  conclusive,  for  we  have  had  no  great 
northers,  the  season  being  unnsually  mild.  But  the  disappearance  of  Bishop's  Ring  for  so  long  a  time 
makes  it  certain  that,  even  if  there  can  be  a  circum-solar  glow  due  to  diffraction  on  ice-particles,  yet 
the  proper  conditions  for  such  a  ring  are  realised  only  rarely,  except  when  there  is  a  great  amount  of 
volcanic  dust  in  the  air." 

♦•G.  H.  STONE." 
"  Colorado  College,  Colorado  Springs." 

Regarding  the  almost  continuous  change  of  tint  of  the  corona  from  orange  to 
dull  reddish-brown  as  time  went  on,  it  appears  that  this  was  most  probably  due 
not  to  any  special  change  in  the  matter  which  caused  it,  such  as  the  introduction  of 
ice  coating  the  dust,  as  is  suggested  by  Professor  Stone,  but  was  simply  a  result  of 
the  corresponding  decline  in  intensity,  allowing  the  less  brilliant  colours  to  be  more 
absorbed  by  the  lower  air.  This  explanation  agrees  with  what  has  already  been  said 
regarding  the  effect  of  change  of  altitude  on  the  brilliancy  of  the  phenomenon. 
There  seems,  therefore,  to  be  no  general  evidence  to  show  that  any  sensible  variation 

•  'Nature,'  vol.  xxxv.  (1887),  p.  581. 


ON  THE   LARGE  CORONA  ROUND   THE   SUN  AND  MOON.  247 

took  place  in  the  appearance  of  the  phenomenon,  as  it  would  have  presented  itself 
from  day  to  day  to  an  observer  on  a  lofty  mountain,  other  than  a  gradual  decline  of 
brilliancy  as  time  proceeded.  This  fact  appears  to  be  of  considerable  importance  in 
relation  to  the  proximate  physical  cause  of  the  phenomenon. 

(3.)  Another  peculiarity  of  this  corona  is,  that  while  ordinary  coronae  of  small 
dimensions  are  frequently  observed  during  the  temporary  passage  of  a  cloud  across 
the  sun's  disc,  this  large  and  nearly  constant  corona  does  not  seem  to  have  been 
vritnessed  previous  to  its  appearance  in  1883,  even  by  those  ordinarily  accustomed  to 
scan  the  heavens. 

Thus  Mr.  Backhouse  says  : — "  It  has  been  habitual  for  me  to  scan  the 
neighbourhood   of  the  sim   for  halos   during   25    years,   and    I  never   observed  it 

previously  to   the  date  mentioned It  is,  therefore,  very  difficult  for  me  to 

believe  that  the  corona  was  visible  in  this  country  much,  if  at  all,  before  last 
November."  {^^) 

MM.  Thollon  and  Perkotin  (^)  speak  to  the  same  eflfect,  in  that,  while  they 
had  previously  always  found  the  sky  clear,  they  "have,  since  November,  1883,  found 
the  sun  surrounded  by  a  circular  zone  of  glowing  white,  very  slightly  tinted  with  red 
outside  and  white  inside." 

The  Rev.  W.  Clement  Ley,  a  world-renowned  sky  observer,  says  that  the  corona 
was  "  unlike  anything  he  ever  saw  before."  And  numerous  other  observers  testify  to 
the  same  effect. 

Professor  von  Bezold  says  that  he  noticed  a  white  glare  round  the  sun  in  former 
years,  but  had  never  before  observed  the  brown  ring.  (®^) 

Obviously,  then,  we  have-here  a  phenomenon  which  for  size,  brilliancy,  univer- 
sality, and  protracted  duration,  appeal's  to  be  unique  in  the  annals  of  Optical 
Meteorology. 

The  Connection  between  the  Corona,  or  Bishop's  Ring,  and  the  Unusual 

Twilight  Glows. 

From  the  simultaneous  appearance  of  these  two  phenomena  in  1883,  it  has  been 
supposed  that  they  were  not  only  due  to  a  common  cause,  but  were  merely  different 
manifestations  of  the  same  physical  effects. 

The  gradual  blending  of  the  former  into  the  latter,  and  the  similarity  of  the 
colour  of  the  outside  of  the  ring,  which  would  be  the  last  to  survive  after  sunset, 
to  that  of  the  final  tint  of  glow  when  near  the  horizon,  tend  to  support  this  notion, 
which  has  been  upheld  chiefly  by  Dr.  Riggenbach*  and  Professor  KiESSLiNG.t 

The  former  refers  to  the  connection  as  follows  : — 

*  *  Beobachtungen  uber  die  DammeniDg.' 
t  *  Die  DammeraDgserBclieiiiungen  im  Jabre  1883/ 
2k2 


248  MR.   E.  DOUGLAS  ARCHIBALD 

"  The  purple  light  begins  to  brighten  up  at  that  part  of  the  sky  where,  at  the 
sudden  disappearance  of  the  sun,  one  would  perceive  the  brightest  part  of  Bishop's 
Ring.  After  two  or  three  minutes,  when  the  extent  of  its  area  has  become  measure- 
able,  it  grows  similar  to  the  extension  of  the  ring  in  size  and  width.  Then  the 
purple  light  increases  both  in  the  direction  of  the  sun  and  in  the  reverse,  but  more 
especially  in  the  latter,  beyond  the  boundary  of  the  ring,  and  attains  its  maximum 
area  simultaneously  with  its  maximum  brilliancy,  when  the  solar  depression  lies 
between  3  J°  and  4^°.  At  this  time  the  purple  glow  occupies  the  whole  of  the  western 
sky,  from  about  6^  up  to  the  zenith,  and  its  seat  is  in  the  atmosphere  from  5  to  13 
kilometres  (16,400  to  42,700  feet).  After  some  time,  when  the  extent  of  surface 
covered  by  the  glow  has  ceased  to  expand,  the  purple  quickly  withdraws  towards  the 
sun,  and  it  disappears,  on  an  average,  when  the  whole  atmosphere  below  6*4  to  9*5 
kilometres  (21,000  to  31,170  feet),  visible  from  the  place  of  observation,  lies  in  the 
shadow.  The  lower  part  of  the  purple  phenomenon  remains  after  the  maximum  of 
light  at  nearly  the  same  distance  from  the  sun,  and  it  is  visibly  nearer  the  sun 
than  the  inner  part  of  the  ring.  At  the  brightening  of  the  purple  glow  still 
higher  portions  of  the  atmosphere  (perhaps  up  to  22  kilometres  =  72,180 
feet)  may  emit  red  rays,  in  which  case  the  exterior  part  of  the  purple  glow 
shrinks  before  extinction  to  about  an  amount  nearly  equivalent  to  the  interior 
part  of  the  ring." 

Prof.  KiESSLiNG  has  closely  investigated  the  cause  of  the  various  phases 
included  under,  and  exhibited  during  the  prevalence  of,  the  unusual  twilight 
phenomena  of  1883-4,  and  appears  to  attribute  them  all,  with  the  exception  of  the 
second  after-glow,  to  diffiaction  through  the  elevate  cloud-haze,  and  to  consider 
them  to  be  continuous  modifications  of  the  physical  conditions  which  gave  rise  to 
Bishop's  Ring  throughout  the  day. 

He  includes  the  ring  as  part  of  the  twilight  phenomenon,  and  after  explaining 
the  excentricity  of  the  sun  with  respect  to  its  circumference  as  it  approaches  the 
horizon,  to  be  due  to  diflfraction  through  layers  of  particles  increasing  in  size  from 
above  downwards,  attributes  the  sudden  appearance  of  the  purple  glow  near  the 
centre  of  the  deformed  ring  to  accumulated  diffraction,  principally  of  the  red  rays, 
through  a  part  of  the  cloud  stratum  which  receives  the  sun's  rays  horizontally  for 
some  considerable  portion  of  its  length.  According  to  this  explanation,  we  should 
have  to  regard  Bishop's  Ring  as  representing  symmetrical  diffraction  through  the  haze 
which,  when  the  sun  sinks  below  the  horizon,  gradually  merges  into  a  special  form  of 
mono-chromatic  diffraction  by  horizontal  rays,  and  still  conclude  that  conditions  which 
might  favour  the  development  of  the  one  phase  would  not  necessarily  promote  the 
brilliancy  of  the  other ;  for,  the  ring,  during  the  day,  would  represent  the  effect  of  the 
general  diffraction  through  the  entire  layer,  and  would  reach  its  maximum  brilliancy 
when  this  layer  reached  its  highest  general  homogeneity  ;  whereas  the  glow  proceed- 
ing from  some  definite  stratum  or  boundary  of  the  haze  might  be  subject  to  certain 


ON  THE  LARGE  CORONA  ROUND  THE  SUN  AND  MOON.         249 

influences*  which   would  affect  portions  of  the  haze  without  altering  its    general 
composition. 

This  might  account  for  the  non-simultaneous  occurrence  of  the  secular  maxima  of 
the  glows  and  of  the  corona,  as  well  as  for  the  fact  that  on  single  days,  "  when  the 
twilight  glows  were  most  striking,  the  ring  was  not  exceptionally  conspicuous/'t 
At  the  same  time,  Professor  Kiessling's  theory  leaves  out  reflection  and  trans- 
mission, which  are  shown  in  Section  I.  (b),  p.  198,  to  account  for  the  main  features  of 
the  glows,  especially  of  the  secondary  glow,  which  was  the  chief  feature  of  the 
present  series. 


In  Opposition  to  the  Views  of  Drs.  Riggenbach  and  Kiessljng. 

Professor  Ilico6,J  in  a  careful  rSsum^  of  his  observations  of  the  twilight 
glows  and  attendant  phenomena  from  December  3rd,  1883,  to  April  30th,  1884, 
concludes  that  the  corona  and  the  primary  glow  are  not  only  separate  phenomena, 
but  are  not  physically  related  to  each  other  in  the  manner  indicated  by  Professor 

KiBSSLING. 

His  reasons  may  be  summarised  as  follows  : — 

(1.)  From  calculations,  taking  account  of  refraction,  the  mean  solar  depression 
at-  the  disappearance  of  the  primary  glow  on  the  horizon  is  9°'5.  On  the  other 
hand,  the  distance  of  the  sim  from  the  region  of  maximum  brightness  of  the  red  in 
the  corona  is  15°*2,  and  from  that  of  its  exterior  boundary  26°'4. 

(2.)  The  appearance  of  diverging  crepuscular  rays  in  the  primary  glow  which 
the  author,  following  other  authorities,  attributes  to  interception  of  the  horizontal 
rays  near  the  earth's  surface  by  distant  mountains,  shows  the  primary  glow  to  be 
due  to  direct  and  not  to  diffracted  light. 

(3.)  The  unequal  rate  of  descent  of  the  edge  of  the  primary  glow,  which  on  the 
average  is  about  1°  in  1  ^  minutes,  and  the  constant  rate  of  descent  of  the  corona, 
which  follows  the  sun  and  descends  from  O'^'l?  to  0°'18  per  minute,  or  1°  in  about 
5^  ininutes.§ 

The  equation  expressing  the  variation  in  the  height  of  the  rosy  twilight  is  thus 
expressed  by  Professor  Ricc6  :  — 

V=  37^-13  sin  ^K, 

*  Such  as  those  mentioned  in  Section  lY. 

t  Dr.  AssMANN,  *Met.  Zeits.,'  vol.  i.  (1884),  p.  196. 

J  ^Biassanto  delle  osservazioni  dei  crepnscoli  rossi,'  Nota  i.,  ii.,  iii.,  1884-5-6,  R.  Aocademia 
dei  liiacei. 

§  Professor  Ricco  does  not  saj  what  happens  to  the  corona  when  the  snn  goes  below  the  horizon. 
Most  observers  saj  that  it  fades  away — whether  subjectively  or  objectively  does  not  seem  quite  clear. 


250  liR.  E.   DOUGLAS  ARCHIBALD 

where  V  represents  the  variation  per  minute,  and  K  the  angular  height  of  the  edge 
of  the  glow  above  the  horizon. 

The  radius  of  the  corona  is  found  to  vary  according  to  a  totally  diflerent 
empirical  law  expressed  by  the  following  equation  : — 

R  =  26°  -  7°16  sin  f  K. 

In  fact  the  radius  of  the  corona  becomes  26°  when  the  sun  is  on  the  horizon,  as 
observed  by  Riggenbach  *  and  others. 

(4.)  The  fact,  already  noticed,  that  in  April,  1884,  when  the  twilight  glows  were 
weak  and  rare,  the  corona  was  at  its  maximum  intensity.  Moreover,  in  January, 
1885,  when  the  extraordinary  glows  had  for  some  time  ceased,  the  corona  was  observed 
several  times  very  distinctly. 

(5.)  Professor  Ricc6  observed  a  special  development  of  the  corona,  viz.,  the  brown 
arc  surrounding  the  sun  at  sunset  from  December,  1883,  to  December,  1884,  fifteen 
times  strongly  marked  (intensity  ^  8),  followed  by  weaker  twilight  glows  (intensity 
^  5) ;  and  Professor  Tacchini  similarly  observed,  from  January  to  December,  1884, 
the  brown  arc  strongly  marked  and  followed  by  weak  displays  of  the  twilight  glows. 
Also  the  former  observed  the  arc  four  times,  and  the  latter  fourteen  times,  not 
followed  by  twilight  glows. 

(6.)  The  descending  corona  is  not  able  to  change,  except  in  a  slight  degree,  its 
form  and  its  dimensions  through  atmospheric  refraction.  The  greater  obliquity  of 
the  diffracting  stratum  is  not  able  to  produce  a  change  in  the  form  and  dimensions  of 
this  coloured  ring,  as  may  easily  be  experimentally  verified  with  a  glass  sprinkled 
with  lycopodium  powder,  and  held  with  varying  obliquity  between  the  eye  and  a 
source  of  illumination. 

(7.)  If  the  rosy  arc  (of  the  twilight  glows)  formed  part  of  a  diffraction  ring,  its 
6olour  would  be  produced  by  the  super-position  of  the  red  and  the  violet  of  two  rings 
of  a  neighbouring  order  ;  and  in  its  spectrum,  besides  the  maximum  in  the  red,  there 
should  be  also  a  maximum  in  the  violet,  which  is  not  the  case. 

Professor  Ricc6,  in  fine,  considers  the  extraordinary  glows  to  have  been  super- 
posed on  Bishop's  Ring,  but  not  produced  either  by  it,  or  by  diffracted  rays,  but,  as 
far  as  the  primary  is  concerned,  by  the  direct  solar  rays. 

Professor  Rtcc6's  arguments  appear  to  demolish  in  great  measure  Professor 
Kiessling's  view  that  the  primary  sunset  glow  is  entirely  due  to  diffraction,  and 
until  they  are  effectively  met  by  the  latter,  we  incline  to  the  view  already  put 
forward  in  Section  I.  (b),  p.  199,  in  which  some  further  considerations  are  urged  against 
the  purely  diffraction  hypothesis,  and  in  favour  of  that  which  accounts  for  both  the 
primary  and  the  secondary  glows  at  sunrise  and  sunset,  mainly  by  reflection 
of  rays  already  tinted  by  diffraction  through,  and  absorption  by,  the  same  stratum, 

*  *  Beobaclitang^n  iiber  die  Dammemng.' 


ON  THE  LARGE  CORONA  ROUND  THE  SUN  AND  MOON.        ^51 

and  the  dust  and  vapour  normally  existing  in  the  lower  atmosphere.  Regarding  the 
disappearance  of  the  ring  at  sunset^  Dr.  Ass2(ann  says : — ^'  The  ring  was  always* 
fainter  a  little  before  sunset,  and  soon  after  was  quite  invisible."  And  again,  Prof. 
CoRNU*  says  : — "  After  simset  the  corona  has  the  appearance  of  a  slight  haze, 
and  gradually  vanishes  ;  the  colours  blend  with  those  of  the  setting  sun,  but  generally 
in  the  higher  regions,  and  they  remind  us  of  the  finest  roseate  hues  of  the  last 
winter's  evenings/' 

General  Opinions  regarding  the  C!orona. 

We  shall  here  give  a  brief  rSsumS  of  some  general  remarks  by  a  few  of  the  lead- 
ing observers  regarding  the  character  and  causes  of  Bishop's  Ring. 

Dr.  AssMANN,t  referring  to  certain  phenomena  witnessed  during  an  ascent  of 
the  Brocken,  says : — "  These  rings  and  wreaths  certainly  gave  one  a  strong  impression 
of  the  existence  of  a  thickly  distributed  dusty  material  sweeping  along  in  close  con- 
tiguity to  the  earth.  That  no  form  of  aqueous  vapour  could  have  caused  this  ring  is 
evident  from  its  optical  peculiarities,  as  also  from  the  instructive  combination  which 
occurred  on  January  13th  between  12  and  2  p.m.  in  the  form  of  a  portion  of  a  regular 
solar  halo  and  of  a  luminous  mock-sun  near  the  brownish-violet  haze  circle,  the 
mock-sun  being  at  least  2^  beyond  the  circle,  The  connection  of  these  coloui-ed  rings 
with  the  abnormal  twilight  phenomena  is  very  probable," 

Professor  H.  Krone,  in  an  article  in  the  '  Met.  Zeitschrift,'  J  says  of  the  red 
region  surrounding  the  twilight  glows  ; — '*  This  red  region  seems  to  be  identical  with 
the  ring  seen  by  Fai^l.  I  cannot,  however,  agree  with  Fall  in  placing  this  ring  in 
the  category  of  solar  and  lunar  halos,  that  is  to  say  among  the  interference  phenomena 

which  are  wont  to  accompany  light  when  transmitted  through  ice-needles 

This  ring  is  uo  other  than  the  red  region  of  the  less  refracted  rays,  yellow,  reddish- 
yellow,  and  red,  caused  through  refraction  of  the  sun's  rays  by  the  atmosphere, 
especially  with  high  atpaospheric  pressure.     .     .     ." 

Professor  von  Bf:zoLp,  ip  a  letter  to  Professor  Kiessling§  (October  24th,  1884), 
says : — 

**  I  have  observed  for  years  the  bright  glow  during  a  high  sun,  and  the  bright 
spot  above  it  when  it  is  below  the  horizon.  I  was,  therefore,  so  far  inclined  to  doubt 
the  argument  which  Clausicjs  brings  forward  in  his  treatise  on  the  colour  of  the 
atmosphere,  that  no  water  globules,  but  only  water  vesicles,  were  present  in  it, 
because,  in  the  first  case,  the  sun  would  always  be  surrounded  by  a  large  pale  sim 
image  of  nearly  60°,  which  is  not  the  fact.     I  often  said  to  myself,  *  Such"  an  image  is 

*  *  Gomptes  Rendus,'  vol.  xcix.,  p.  490. 
t  *  Met.  Zeitschrift,'  vol.  i.  (1884),  p.  197. 

t  lUd,^  vol.  i.  (1884)  ,p.  277.       *  Bericht  iiber  die  vulkamsche  Ausbniche  des  Jahrea  1883,*  von 
Dr.  Neumatkr. 

§  '  Das  Wetter,'  1884,  p.  178. 


252  MR.  E.  DOUGLAS  ARCHIBALD 

actxially  present,  although  its  extension  does  not  quite  correspond  with  the  conditions 
of  the  theory  ;  and  I  have  for  years  inferred  a  connection  between  this  glow  and  the 
purple  light,  but  since  no  one  took  any  interest  in  my  twilight  observations  I  let  the 
fact  drop,  and  confined  myself  to  occasional  observation. 

"  On  the  other  hand,  in  spite  of  the  close  attention  I  bestowed  on  this  bright 
shine,  I  have  never  before  observed  the  brown  ring,  which  surprised  me  for  the  first 
time  on  December  1st,  1883,  the  same  day  on  which  the  unusual  twilight  glows 
appeared,  and  which  I  have  now  very  often,  particularly  during  this  autiunn,  seen 
with  wonderful  development.  I  have  also  for  the  first  time  observed  the  reddish 
colours  in  the  interstices  between  the  clouds  [in  daytime]  during  this  last  winter." 

Professor  Le  Contb,  of  California,  (^^)  regards  the  ring  as  a  difiVaction  pheno- 
menon, but  mixed  with  an  imperfectly  developed  ice-halo,  and  hence  accounts  for  the 
feebleness  and  blending  of  the  tints. 

M.  Thollon  {^)  says  that  the  phenomenon  was  visible  at  Nice  from  November, 
1883,  to  July,  1884,  and  that,  as  he  was  quite  certain  he  had  never  observed  similar 
phenomena  in  former  years,  he  concluded  that  some  remarkable  change  had  occurred 
in  the  atmosphere  &om  that  date  in  that  locality.  He  says  also  that  the  corona  is 
evidently  produced  by  diffraction  through  some  light  powder. 

Professor  Forel,  (®^)  from  an  examination  of  European  records  only,  concluded 
that  an  immense  dust-cloud  existed  suspended  in  the  air  over  Central  Europe. 

Prof.  CoRND*  remarks  that,  in  favourable  circumstances,  the  order  of  the  colours 
in  Bishop's  Ring  is  as  follows  : — 

*'  Proceeding  from  the  centre  outwardly,  clear  azure  blue,  neutral  grey,  brown^ 
yellow,  orange-yellow,  coppery-red,  purple-red,  and  dull  violet,  which  is  analogous  to 
the  succession  of  the  colours  of  the  first  ring  of  diflfraction  coronse  presented  by 
thin  clouds.  We  can  often  make  a  direct  comparison.  These  vivid  hues  are  not 
always  produced  when  the  spaces  open  on  the  corona^,  as  a  second  condition  is 
necessary,  viz.,  that  the  hazy  reds  seen  shall  be  in  the  shade,  otherwise  the  colours 
are  flooded  with  white  light.  This  condition  is  evident  when  we  follow  the  sun's 
beams  across  those  spaces,  since  it  is  only  beyond  the  reach  of  these  rays  that  these 
red  tints  of  fiery  lustre  are  observed.  These  observations  seem  to  indicate  that  the 
phenomenon  has  its  fifeat  far  above  the  cumulus  (perhaps  above  the  cirrus),  and  that 
it  acquires  its  most  extraordinar}>  intensity  when  viewed  from  spots  where  there  is 
no  terrestrial  haze." 

Professor  Piazzi  Smyth  says  {^)  ; — **  That  such  appearances  [those  noticed  by 
him  on  September  3rd,  1884,  and  by  Mr,  Backhouse,  in  the  Alps,]  were  produced  by 
solid  particles  in  a  cold  state,  and  not  by  any  new  gas  introduced  into  the  atmosphere, 
seems  to  be  borne  out  by  three  sets  of  rather  extensive  solar  spectroscopings  which 
I  have  lately  cai:ried  out;  for  while  there  does  not  seem  to  be  a  single  new  line 
amongst  the  thousands  of  old  ones,  as  far  as  I  have  yet  examined  the  observations, 

*  *  Comptes  Rendus,*  vol.  xcix.,  p.  490. 


/^ 


ON   THE   LARGE   CORONA   ROUND   THE    SUN   AND   MOON.  253 

there  is  only  too  abundant  evidence  of  a  continued  dulling  of  the  light  of  the  sun's 
continuous  spectrum  along  its  range. 

"This  effect  is,  of  course,  more  conspicuous  in  the  faint  regions  at  each  end 
than  in  the  bright  middle,  and  appears  to  be  testified  to  undeniably  by  the  following 
differential  observations,  viz.,  that  with  a  prismatic  apparatus  wherewith  I  could  see 
lines  in  the  bright  regions,  say,  of  B,  C,  and  D,  rather  better  than  I  could  with 
somewhat  similar  but  darker  prisms  in  1877,  I  could  not  see  Brewster's  line  Y,  and 
its  companion  groups  in  the  very  faint  ultra-red,  so  well  as  I  did  then ;  and  could  not 
see  the  further-away  line  X  at  all,  though  in  1877  it  was  not  only  clear  enough,  but 
far  fainter  lines  on  each  side  of  it  were  visible,  and  micrometrically  measurable. 
Neither  in  1884  have  I  been  able,  with  the  same  eye, and  instrument,  to  see  anything 
at  the  violet  end  of  the  spectrum  of  the  grand  banded  lines  H  and  K,  though  they 
formed  a  daily  subject  of  observation  in  1877.  In  1856,  I  remarkably  appreciated 
that  an  ascent  to  1 1,000  feet  on  the  Peak  of  Teneriffe  enabled  H  and  K  to  be  seen 
with  pecuUar  distinctness  and  fine  resolution  of  much  of  their  haze  at  lower  levels 
into  sharp  lines,"  &c. 

These  observations  are  evidently  important,  not  only  in  their  negative  bearing 
on  the  cause  of  the  corona,  but  in  their  positive  bearing  on  the  general  absorption 
exercised  by  the  haze. 

Prof.  KiESsrjNG  has  studied  the  diflfraction  phenomena  in  the  laboratory  and 
also  in  the  operations  of  nature,  and  we  shall  here  quote  the  results  of  some  of  his 
experiments  and  remarks,  as  they  have  a  very  important  bearing  on  the  cause  of  the 
corona  as  well  as  on  that  of  the  entire  range  of  optical  effects  which  began  in  August, 
1883. 

His  experiments  *  (a  detailed  account  of  which  is  appended  to  this  section,  p.  258) 
lead  to  the  following  conclusions  : — 

(1.)  That  when  the  particles  are  of  the  same  size,  a  condition  which  is  not 
ordinarily  .fulfilled  in  smoke  and  cloud,  either  dust,  or  dust  and  vapour  together, 
transmit  with  solar  light  coloured  coronae  ;  but  that  when  the  particles  are  of  different 
sizes  the  diffraction  image  is  colourless. 

(2.)  That  when  the  air  is  filtered  from  dust,  and  vapour  is  introduced  into  the 
diffraction  chamber,  and  the  temperature  is  lowered,  no  trace  of  diflfraction  rings  is 
visible  with  transmitted  Kght. 

(3.)  On  introducing  ordinary  (and  therefore  dusty)  air  into  the  chamber,  and 
lowering  the  temperature  and  pressure,  a  ring  with  a  bluish  interipr  and  a  broad  red 
border  is  obtained,  very  similar  to  the  corona  of  1883.  The  finest  effects  are 
obtained  by  starting  with  a  maximum  of  vapour  tension,  the  colours  changing  as 
the  temperature  and  pressure  are  lowered,  showing  two  marked  stages. 

*  Partly  described  in  the  *  Meteor.  Zeitschr.,'  vol.  i.,  1884,  and  partly  in  his  pamphlet,  •  Die 
DftmmemngsergoheinungOD  im  Jahre  1883/     Leipzig,  1885. 

2   L 


254  iiK.   E..  DOUGLAS  ARCHIBALD 

In  the  first,  the  order  is  as  follows,  from  the  centre  outwards  : — "Pale  lilac,  pale 
bluish-violet,  bright  blue,  bluish-green,  emerald-green,  yellowish-green,  greenish- 
yellow,  bright  orange,  dark  orange,  pale  scarlet-red,  pale  purple-red." 

In  the  second,  when  the  temperature  and  pressure  are  much  lower,  the  order  of 
the  colours  from  the  centre  is  as  follows : — "  Pale  purple-red,  stone-green,  luminous 
olive-green,  yellowish-green,  luminous  bronze-yellow,  orange." 

To  obtain  a  bluish  central  field  with  a  broad  reddish-brown  ring,  a  little  smoke 
must  be  added  to  the  vapour. 

As  Prof  KiESSLiNG  considers  the  entire  series  of  optical  effect.s  which  began  in 
August,  1883,  to  be  due  to  diffiuction,  we  cannot  here  refer  to  his  general  views 
regarding  the  connection  between  tliese  and  the  eruption  of  Krakatoa ;  but  may 
notice,  with  reference  to  the  corona  alone,  that,  according  to  him,  the  phenomenon 
may  have  been  produced  either  by  diffraction  through  dust  alone,  or  through  a 
homogeneous  cloud  formed  round  the  finest  dust  particles. 

The  necessary  homogeneity  in  the  former  case,  he  thinks,  may  have  arisen  from 
the  heavier  particles  of  the  dust  clouds  ejected  from  the  volcano  having  been  sifted 
out  by  gravitation,  leaving  the  remainder  so  nearly  of  the  same  size  that  they  were 
capable,  by  themselves,  of  producing  the  coloured  difiraction  phenomena.  He 
mentions,  also,  having  produced  clearly  coloured  diffiraction  rings  with  finely  sifted 
and  pulverised  cement. 

Regarding  the  general  question  as  to  whether  the  haze,  or  whatever  produced 
the  corona,  was  solely  dry  dust  or  smoke,  or  partly  or  entirely  minute  ice  spiculae 
formed,  as  Aitken  would  tell  us  they  generally  are,  round  dust  nuclei,  the  corona 
alone  does  not  give  us  a  decided  answer,  since  diffraction  through  such  spiculffi 
might  produce  a  corona  of  the  same  angular  dimensions  as  that  produced  by  dust  of 
the  same  size  and  shape ;  and  the  fact  that  the  angular  diameter  of  the  corona  in 
the  present  case  was  almost  exactly  the  same  as  that  of  the  refraction  halo  for  ice 
prisms,  viz.,  45°,  might  be  thought  a  suflScient  reason  for  the  absence  of  the  latter. 
Dr.  Assmann's  observation,  however,  quoted  above,  of  a  solar  halo  appearing  on 
January  13th,  1884,  seems  to  make  it  plain  that  if  there  had  been  a  halo  produced 
in  the  haze,  which  was  the  seat  of  the  ring,  it  would  have  been  at  once  detected 
as  a  separate  phenomenon.  If,  therefore,  the  corona  was  formed  by  ice  prisms  sur- 
rounding dust  nuclei,  it  seems  strange  that,  while  the  corona  was  always  visible, 
there  was  no  trace  of  a  refraction  halo  in  the  same  stratum,  as  we  should  be  led  to 
expect. 

Besides  this  negative  evidence,  there  are  many  other  considerations  in  favour  of 
the  notion  that  the  haze  which  caused  all  the  unusual  optical  phenomena  was 
composed  chiefly  of  dry  dust.  Some  of  these  have  been  already  noticed  in  Section 
I.  (b),  p.  195,  in  which  certain  peculiarities  presented  by  the  glows  appear  to  find 
their  explanation  solely  on  this  hypothesis. 


J 


ON   THE  LARGE   CORONA  ROUND  THE   SUN  AND  MOON.  255 

We  may  here  add  a  few  more  : — 

(1.)  The  fact  that  in  cirrus,  or  cirro-stratus  ice-haze,  in  which  alone  refraction 
halos  are  seen,  coronse  are  seldom  if  ever  observed.  On  the  other  hand,  in  the  lower 
clouds,  where  water  occurs  in  minute  spherules  (water  dust),  coronae  are  frequently 
obsei*ved*  Kaemtz  *  says  : — "  CoronsB  occur  in  the  middle  of  cumulus,  halos  in  cirrus/' 
Now,  it  can  scarcely  be  doubted  that  any  water  vapour  which  occurred  in  the  cloud 
haze  would,  at  an  elevation  of  from  60,000  to  120,000  feet  or  more,  be  entirely  frozen 
into  ice-spiculae  resembling  those  in  the  cirrus.  We  should,  therefore,  by  all  analogy 
and  experience,  have  expected  halos  rather  than  coronae  to  prevail  in  this  elevated 
stratum.  Instead  of  this,  however,  we  find  no  traces  of  halos  in  the  haze,  but  a  per- 
sistent brilliant  and  immense  corona  such  as  has  never  before  been  witnessed.  In  the 
absence,  therefore,  of  any  special  evidence  to  show  that  ice-spiculae  could  be  formed 
and  continue  at  such  an  elevation  (which  on  meteorological  and  physical  grounds  is 
very  improbable  t),  and  of  so  minute  a  size  as  to  produce  so  large  a  corona,  or  that 
they  should  give  rise  to  a  corona  in  preference  to  a  halo,  contrary  to  what  occurs  in 
the  cirrus  and  cirro-stratus,  the  constant  occurrence  of  this  large  corona  for  two 
or  three  years  must  alone  be  considered  as  evidence  in  favour  of  the  haze  being 
composed  chiefly  of  dust. 

(2.)  The  remarks  of  Mr.  Attken,  in  his  paper  referred  to  in  Section  IV.,  p.  346, 
as  to  the  sifting  rather  than  absorbing  influence  of  the  haze,  which  he  proved  by  means 
of  the  polariscope. 

(3.)  The  peculiar  effect  of  the  haze  on  astronomical  definition,  and  the  effects 
witnessed  diu:ing  lunar  eclipses  (Section  I.  (d),  p.  225) ;  and 

(4.)  The  general  evidence  from  Mr.  Verbeek's  report,  that  the  ejecta  from 
Krakatoa  during  its  eruption  on  August  26th  and  27th,  were  mainly  fine  and  dry 
pumiceous  dust,  the  rain  of  mud  occurring  only  locally  and  temporarily,  more  than 
20  hours  after  the  principal  explosions  had  commenced.  | 

Summary  of  Part  IV.,  Section  I.  (e). 

Taking  all  the  facts  regarding  the  corona,  or  Bishop  s  Ring,  together,  we  arrive  at 
the  following  conclusions  : — 

(1)  That  the  date  on  which  it  was  fii-st  distinctly  seen  was  September  5th,  1883, 
by  Mr.  Bishop  at  Honolulu,  after  which  it  appeared  at  most  places  where  the  other 
optical  effects  were  witnessed  : 

(2)  That  its  principal  colours  were  bluish-white  in  the  centre,  shading  off  into 
a  reddish-brown  border,  the  diameter  of  the  inner  space  being  about  21^,  and  the 
entire  ring,  to  the  external  boundary  of  the  red,  about  45°  30'.      Round  the  moon  the 

♦  'Meteorology,*  translated  by  Walker,  p.  431. 
t  See  "  General  Analysis,'*  Section  VII. 
X  This  point  is  further  considered  in  Section  VI T. 
2  L  2 


256  MR.   E.   DOUGLAS  AECHIBALD 

only  colour  distinguishable  was  a  pale-reddisb  circular  boundary,  the  apparent  diameter 
of  which  was  somewhat  smaller  than  that  round  the  sun  : 

(3)  That  when  it  was  visible  it  appeared  all  day  from  sunrise  to  sunset  under 
favourable  conditions  : 

(4)  That  it  reached  its  maximum  intensity  about  the  spring  of  1884,  since  which 
time  it  gradually  declined  in  brilliancy  and  visibility,  down  to  June,  1886.  Since 
this  latter  date  it  has  not  been  seen  even  by  one  of  its  most  careful  observers, 
Professor  Rioc6 : 

(5)  That  it  was  best  seen  at  great  altitudes ;  and  near  the  earth  it  was  best  seen 
on  days  when  the  air  was  free  from  ordinary  dust  or  smoke  : 

(6)  That  it  appeared  to  be  independent  of  all  ordinary  atmospheric  disturb- 
ances : 

(7)  That  it  was  most  probably  formed  in  the  haze  stratum,  which  proximately 
caused  the  twilight  glows  and  other  optical  phenomena  : 

(8)  That  though  a  white  glare,  resembling  its  inner  portion,  had  been  observed 
in  previous  years  by  Professor  von  B£Z0LD,  he  had  never  before  seen  a  corona  of  tho 
same  size  and  with  the  marked  reddish  border  : 

(9)  That  it  was  a  diffi*action  corona  produced  by  the  accompanying  haze,  and 
that  its  great  size  proves  this  haze  to  have  been  composed  of  exceedingly  small 
particles : 

(10)  That  the  order  of  'the  colours  shows  it  to  have  been  most  probably  a 
diffraction  ring  of  the  first  order  :* 

(11)  That  the  occurrence  of  a  corona  in  so  elevated  a  region,  as  well  as  the 
general  absence  of  accompanying  refraction  halos,  tends  to  show  that  the  particles 
through  which  the  difiraction  took  place  were  solids,  and  dust  rather  tbm  ice  : 

(12)  That  while  the  corona  was  associated  with  the  twilight  glows  and  coloured 
Sims  in  being  produced  by  the  same  elevated  haze,  it  was  physically  distinct  firom 
either,  and  probably  contributed  only  very  slightly  to  the  glows,  after  the  sun  sank 
below  the  horizon : 

(13)  That,  from  Dr.  Kiessling^s  experiments,  it  appears  that  exactly  similar 
phenomena  can  be  produced  on  a  small  scale  by  diffraction  of  the  sun's  rays  through 
minute  dust,  or  vapour  momentarily  condensed  in  ordinary  dusty  air. 

Thb  Size  of  the  Particles  which  Produced  the  Large  Corona,  or 

Bishop's  Ring. 

The  size  of  the  particles  Jias,  by  two  observers,  been  estimated  as  follows : — 

Millimetre.  Inch. 

(«7)  Professor  FoREL     at     -003         =  -00011 

(«8)  Herr  Flogel         at     '001         =         -00004 

•  See  Prof.  Cornu,  p.  252,  and  Professor  Ricco,  in  his  paper  already  quoted. 


ON  THE  LARGE  CORONA  ROUND  THE  SUN  AND  MOON. 


257 


The  writer  of  the  present  section,  taking  the  mean  value  of  the  inner  and  outer 
diameters  of  the  corona  to  be  21°  and  45°  30',  and  taking  the  former  to  represent  the 
position  of  the  bright  violet  and  the  latter  that  of  the  red  ring,  obtains  the  following 
results : — 

The  formula  employed  is — 

Sin^=N^, 

where — 

d  =  the  diameter  of  a  dust  globule  ; 

D=  the  angular  diameter  of  the  ring  of  the  particular  colour  chosen ; 
X  =  the  wave-length  of  the  colour  ; 

N=  a  constant  whose  values  for  the  rings  of  the  first  and  second  orders  are 
07655  and  17571  respectively.* 

We  shall  give  the  values  for  the  first  and  second  orders,  though  everything 
points  to  the  probability  of  the  entire  corona,  as  seen,  belonging  to  the  first  order. 

The  radius  to  the  middle  of  the  ring  is  taken  to  be  15°  10',  the  value  given  by 
Professor  Eicc6  for  the  position  of  maximum  intensity.  Since  in  diffracted  spectra 
the  middle  of  the  spectrum  coincides  with  the  position  of  the  rays  of  maximum 
intensity,  this  will  give  us  values  more  probably  correct  than  either  the  radius  to 
the  inner  or  to  the  outer  boundary,  both  of  which  were  less  definitely  marked. 

Diameter  of  the  Particles  (supposed  Spherical)  causing  Bishop's  Ring. 


•  • 

•  • 

Isfc  Order. 

2nd  Order. 

Inner  diameter  21° 
Middle       „        30°  20'    . . 
Outer         „        45°  30'    . . 

•00165  mm. 
•00162     „ 
•00160      „     • 

•00379  mm. 
•00376     „ 
•00346     „ 

Meana 

•00159  mm. 
=  •00006  in. 

•00367  mm. 
=  •00014  in. 

It  will  be  noticed  that  these  values  are  very  fairly  accordant,  the  discrepancies 
showing  that,  if  anything,  the  internal  radius  was  measured  somewhat  too  small  or 
the  outer  too  large,  but  the  total  difference  is  very  little. 

K  we  take  the  mean  of  both  the  values  from  all  three  diameters  for  the  first  and 

second  orders,  we  get  "0001  inch,  which  is  the  same  as  that  given  by  Professor 

FoREL ;  but  as  we  take  the  ring  to  have  been  of  the  first  order,  we  shall  adopt  as 

the  most  probable  value  '00006  inch.t 

E.  Douglas  Archibald. 

*  For  the  yalnes  of  these  confltants  the  writer  is  indebted  to  Professor  Stokes,  P.B.S. 
t  This  is  about  three  times  the  mean  length  of  a  wave  of  light.     Some  of  the  particles,  however 
maj  have  been  smaller  than  the  length  of  a  wave  of  red,  and  perhaps  even  of  violet,  light. 


258  MR.  E.  DOUGLAS  ARCHIBALD 


APPENDICES   TO   CORONA  SECTION. 

Discussion  and  Account  of  Experiments  in  Connection  with  Diffraction  Coronce,  and 

Bishop's  Ring,  by  Pro/essai^  Kiessling.* 

When  the  sun's  rays  are  passed  through  a  cloud  formed  of  sulphate  of  ammonia,  formed  by 
sulphurous  acid  and  ammonia  vapour,  an  image  is  formed,  which  rapidly  changes  in  colour  from  a 
dark  copper,  through  violet  and  crimson,  to  a  brilliant  azure  blue.  In  a  moist  air  these  chaoges 
are  more  rapid  than  in  dry.  Clouds  formed  of  phosphoric  acid,  sal  ammoniac,  and  gunpowder 
smoke  give  the  same  results.  In  the  case  of  the  sal  ammoniac  cloud,  steam  intensifies  the  blue, 
and  causes  it  to  occur  earlier;  a  steam  or  aqueous  vapour  cloud  in  air  gives  rise  to  colours  between 
brownish-red  and  dark  grey -blue.  The  green  colour  could  not  be  artificially  produced.  Laugikb 
made  an  observation  on  the  island  of  Ouessant  [apparently  a  blue  sun]  (*  Comptes  Rendus,'  vol.  39)  in 
1854,  which  prompted  the  accurate  research  into  the  action  of  aqueous  vapour  in  causing  blue  sun, 
made  by  Foubnbt  in  1858  and  1859  (*  Comptes  Rendus,'  vols.  47  and  48),  and  by  Lissajous,  March, 
1858.  FouBNET  found  that  the  atmosphere  was  never  pure  white  when  aqueous  vapour  was  preaeut, 
but  was  always  more  or  less  orange  or  blue.  Cumulus  clouds,  increasing  in  thickness  from  the  cir- 
cumference to  the  centre,  showed  successive  phases  of  the  phenomenon  as  the  wind  wafted  them 
along.  In  most  cases,  if  the  sun  was  covered  or  dimmed  by  clouds,  the  borders  of  the  neighbouring 
clouds  were  gilded,  and  the  clouds  themselves  coloured  orange.  Between  the  orange-coloured  zone  and 
the  sun's  radiating  disc  is  a  blue  space ;  and  if  the  sun  passes  behind  a  cloud-veil  with  more  or  less 
sharp  contours,  these  become  blue  or  dull  white,  or  orange,  according  to  the  density  of  the  obscuring 
cloud.  (See  also  '  Phil.  Mag.,'  vol.  58,  1821,  p.  234.)  [He  then  refers  to  the  dimmed  and  coloured  suns 
seen  in  1831  and  1883,  which,  he  says,  were  apparently  due  to  volcanic  dust  clouds.] 

If  the  diJSraction  chamber  be  filled  with  moist  air  which  has  been  thoroughly  filtered  and  freed 
from  dust,  and  the  temperature  be  lowered,  then  a  cloud  is  formed  which  is  visible  only  in  direct 
sunlight.  It  consists  of  very  minute,  very  scattered,  cloud  particles,  which  do  not  produce  the  slightest 
trace  of  coloured  difPraction  rings  with  transmitted  light ;  evidently  because  there  are  too  few  of  them  in 
the  chamber.    A  slight  cloud  is  formed  in  dustless  air,  which  resolves  itself  into  small  rain  without  cloud. 

On  introducing  a  little  ordinary  air  into  the  chamber,  a  smoky  cloud  is  formed  at  once,  in 
addition  to  the  large  drops  of  rain.  If  through  this  mixture  of  cloud  and  rain  we  look  at  a  screen  of 
tissue  paper  placed  immediately  behind  the  diaphragm  of  the  heliostat,  which  is  about  2  cm.  broad,  a 
yellowish-brown  halo,  with  reddish-brown  boundaries,  is  formed,  just  of  the  colour  and  size  of  the 
ordinary  lunar  halo.  If  a  diminution  in  pi*e88ure  be  made  to  occur  simultaneously  with  a  sadden 
lowering  of  temperature,  then  larger  and  more  distinctly  coloured  diffraction  rings  are  formed, 
without  the  already  existing  diffraction  image  being  in  the  slightest  degree  altered.  Hence  it  follows 
that  in  the  above-described  process  of  condensation,  the  first  formed  cloud -particles  are  not  vesicles 
but  true  water  droplets ;  for  if,  under  ordinary  atmospheric  pressure,  the  first  cloud- formation 
conaisted  of  vesicles,  a  rapid  decrease  of  from  80  to  120  mm.  of  pressure  would  necessarily  cause 
a  rapid  expansion  of  the  vesicles  and  a  correspondingly  rapid  decrease  in  the  diameter  of  the  first 
diffraction  nngs  formed  thereby.  But  it  is  not  so.  At  the  first  moment  of  decrease  of  pressai-e 
there  is  a  broad  central  space  which  becomes  a  trifle  smaller  only  during  rapid  colour  changes,  whereby 
it  forms  a  group  of  concentric  distinctly  coloured  rings,  so  that  in  the  course  of  one  or  two  seconds, 
two  diffraction  figures  appear,  one  over  the  other,  differing  greatly  in  size  and  colour  (the  second  being 
the  less  vivid  of  the  two).  With  continued  decrease  of  pressure  the  diameter  of  the  two  ring  systems 
gradually  diminishes  simultaneously.  Clausius  has  thoroughly  discussed  this  subject  in  his  'Die 
Lichterscheinungen  der  Atmosphare  '  (Leipzig,  1850,  pp.  392,  396;  *Pogg.  Ann.,*  vols.  76,84,  and  85);  and 

*  Abridged  and  translated  from  *  Met.  Zeitschrift,'  vol.  (1884;,  pp.  117  ei  srq. 


ON   THE   LARGE   CORONA   ROUND   THE   SUN   AND   MOON.  259 

Bubichabt«Jbzler  has  more  recently  (*Pogg.  Ann.,'  vol.  145)  endowed  the  vesicnlar  theory  with  decisive 
importance.  The  formation  of  bright  diffraction  colours  is  in  complete  accordance  With  Fraunhofeb*8 
theory,  that  they  necessitate  clouds  formed  of  particles  of,  as  nearly  as  may  be,  the  same  sise.  This 
presupposes  the  presence  of  a  fine  dust,  which  is  ordinarily  existent  in  the  air  of  rooms,  and  in  the 
atmospheric  layers  nearest  the  earth,  and  appears  to  be  most  efficient  in  acting  upon  light  when  the  air 
is  saturated. 

This  is  most  readily  effected  when  the  air  has  passed  through  water  at  30°  to  40°  C,  before  being 
introduced  into  the  difiraction  chamber,  and  when  the  decreased  pressure  causing  a  redaction  of 
temperature  is  spread  over  at  least  a  minute.  When  these  conditions  prevail,  the  development  of  colour 
is  so  intense  that  a  sectional  figure  of  the  cone  of  diffraction  rays  emitted  by  the  bell-glass  is  formed 
upon  a  screen  of  white  tissue  paper,  placed  at  a  distance  of  1  metre  .  .  •  the  colours  of  which,  in 
specially  favourable  circumstances,  that  is,  when  the  constituent  particles  of  the  cloud  are  as  nearly  as 
possible  of  the  same  siae,  rival  in  intensity  those  of  a  solar  spectrum  of  large  dispersion  viewed  objectively. 
The  amplitude  of  this,  depending  upon  the  size  of  the  cloud  corpuscles,  varies  between  10°  and  30°. 
In  consequence  of  the  intimate  dependence  of  the  intensity  of  the  light  upon  the  uniform  structure 
of  the  colour-producing  cloads,  great  care  is  required  in  the  objective  representation  of  intensely  bright 
diffraction  images ;  since  only  dull  colours  are  formed  when  the  water  is  too  hot  or  too  cold. 

The  diffraction  image  undergoes  a  remarkable  change  of  colour  when  the  pressure  is  continually 
diminished.  This,  however,  occurs  only  in  the  incipient  stage  of  cloud  formation,  and  generally 
presents  two  periods,  at  the  termination  of  which  the  colour  remains  constant ;  yet  the  last  phases  of 
the  first  period  are  so  constant  under  some  conditions,  that  there  is  no  change  of  colour  with  a  decrease 
of  10  to  20  mm.  in  pressure,  and  consequently  of  1°  to  2°  C. 

The  rapidity  of  the  succession  of  colours  depends  upon  the  degree  of  humidity,  and  upon  the  rate 
at  which  the  temperature  is  lowered,  which  would  be  materially  influenced  by  the  walls  of  the  relatively 
small  diffraction  chamber.  The  dependence  of  the  colour  tone  upon  these  two  factors  is  very  close. 
An  accurate  determination  of  it  will  require  further  investigation.  The  colour  changes  are  perceived  in 
the  central  area,  as  well  as  in  the  surrounding  concentric  rings.  This  can  be  distinctly  observed — 
objectively  by  means  of  the  image  cast  upon  a  transparent  screen,  or  subjectively  by  direct  observation 
of  the  sun's  light  which  has  passed  through  the  diffraction  chamber,  or  by  interposing  a  transparent 
screen  of  tissue  paper  about  2  cm.  in  diameter,  in  front  of  the  heliostat.  The  observation  of  the  colour 
development  in  direct  sunlight  is  attended  with  difficulty,  partly  because  the  eyes  suffer  from  making 
such  observations,  but  mainly  because  the  images  are  so  transitory,  owing  to  the  formation  of  air-layers 
of  different  temperatures  which  mix  together,  that  the  originally  coloured  concentric  rings  of  the 
diffraction  image  are  soon  lost  in  the  brighter  but  distinctly  coloured  reciprocally  penetrating  cloud- 
image.  On  this  account  I  have  investigated  the  colour  changes  in  the  last-mentioned  ways  only. 
The  colours  then  always  appear  less  bright,  and  also  undergo  a  modification,  but  not  an  important  one, 
in  the  higher  tones  of  colour,  namely,  the  yellow  and  the  red  shades.  In  the  presence  of  the  electric 
light  the  development  of  colour  is  especially  interesting  in  modifications  between  blue  and  violet. 

At  the  very  commencement  of  the  depression  of  temperature  there  is  originated  a  white,  silvery 
shining,  excessively  thin,  and  thoroughly  transparent  cloud,  of  which  the  first,  very  transitory,  colour 
appears  to  be  a  dull  violet ;  the  diameter  of  the  central  field  varies  according  to  the  amount  of 
vapour  present,  between  15°  and  60°.  Then  the  following  colours  rapidly  succeed  each  other  in  the 
central  area  :  dull  lilac,  dull  blue-lilac,  brilliant  clear  blue,  bluish-green,  emerald-green,  yellowish- 
green,  greenish-yellow,  bright  orange,  dull  orange,  dull  scarlet,  and  crimson-red.  This  closes  the 
first  period.  Each  sacceeding  colour  appears  to  spread  over  the  preceding  one,  which  then  contracts 
in  diameter,  so  that  an  image  is  formed  composed  of  richly  coloured  concentric  rings.  This 
encroachment  of  colour,  however,  does  not  proceed  uniformly,  but  some  rings  sometimes  become  so 
narrow  as  to  be  indicated  only  by  a  transition  tint,  so  that  the  succession  of  colon rs  in  the  spectrum 
is  apparently  interrupted.  I  have  not  yet  been  able  to  ascertain  the  cause  of  this  abnormal  occurrence, 
which  must  stand  over  for  future  investigation. 


260  MR.  E.   DOUGLAS   ARCHIBALD 

All  the  colours  are  mixed,  but  are  suffused  with  such  a  peculiar  soft  glowing  light  that  it  is 
exceedinglj  difficult  to  represent  them  hj  means  of  water-colours.  The  estimation  of  the  colours  in  the 
several  phases  of  the  development  is  rendered  especially  difficult,  partly  because  the  ooloar  is  rapidly 
dulled  in  consequence  of  the  formation  of  fresh  cloud-particles  from  the  continuously  wet  walls  of  the 
diffraction  chamber,  and  partly  because  a  constant  change  is  proceeding  in  the  rings  as  well  as  in  the 
central  area,  owing  to  the  changes  of  temperature.  A  stationary  condition  first  supervenes  at  the  end 
of  this  period.  This  is  pre-eminently  the  phase  of  the  colour  development,  during  which  the  omtral 
fijld  is  orange,  the  first  ring  a  bright  green,  and  bluish-green  ;  and  the  second,  if  of  moderate  breadth, 
comprises  all  shades  between  blue-violet  and  crimson-red.  The  whole  aperture  of  the  cone  issuing 
from  the  diffraction  appears  to  be  nearly  40°,  and  in  especially  favourable  circumstances,  that  is  when 
the  cloud  is  very  homogeneous,  it  amounts  to  70°.  If  we  allow  sal  ammoniac  clouds  to  rise  within 
this  cone,  then  these  appear  to  be  green-blue  or  pnrple-red,  as  soon  as  they  catch  the  rays  of  light. 
This  phase  also  is  nearly  stationary ;  dull  crimson  in  the  central  area,  surrounded  by  a  broad  green 
and  a  narrow  blue-violet  ring.  This  phase  may  often  be  watched  for  15  or  20  seconds  without 
showing  any  change. 

The  second  period  of  coloar-change  in  the  central  area  shows  a  much  nanx>wer  rang^  of  colom^ 
which  now  always  partake  of  the  character  of  mixed  colours  overlapping  one  another.  The  colours 
are :  crimson-red  (with  an  approximately  violet  glow),  stone-gray  (with  an  approximately  green  glow), 
bright  olive-green,  yeHowish-green,  bright  bronxe-yellow,  and  orange.  If  the  decrease  of  temperature  (as 
a  consequence  of  diminution  of  pressure)  be  continued,  the  orange  becomes  more  red  and  bluish  in 
tone,  so  that  there  is  a  sudden  renewal  of  the  colour  which  characterises  the  beginning  of  the  second 
period,  crimson-red ;  then  a  repetition  of  the  second  period  sets  in,  but  in  gradually  fading  colours, 
which  become  less  distinct  as  the  density  of  the  cloud  increases. 

As  aforesaid,  the  development  of  colours  is  closely  dependent  on  the  humidity ;  so  that  when  there 
lias  been  a  reduction  of  temperature  after  the  introduction  of  rapidly  succeeding  streams  of  diy,  dusiy 
air,  and  of  air  supersaturated  with  moisture  by  passage  through  hot  water,  there  is  often  a  parti- 
coloured mixture,  lasting  10  to  15  seconds,  glowing  with  all  the  colours  of  the  spectrum,  and  forming  a 
vortex  of  cloud  particles,  in  which  the  contrast  between  purple-red  and  emerald-green  interpenetrating 
cloud  masses  is  quite  sharply  defined  on  opposite  sides  of  the  cloud  mass.  This  seems  to  represent  the 
same  condition  of  things  as  occurs  in  the  well-known  Brasilian  twilight  phenomenon  called  ^'  arrtbolj" 
which  has  been  fully  described  by  Bubkhabt-Jezleb. 

The  dependence  of  the  colours  upon  the  specific  nature  of  the  medium  is  particularly  well  displayed 
if  the  upper  part  of  the  diffraction  chamber  be  warmed  by  means  of  a  gas  flame.  This  checks  the 
formation  of  the  large  cloud  pai*ticles  in  the  upper  part  of  the  glass.  If,  now,  the  temperature  be 
lowered,  and  the  diffraction  image  be  such  that  the  central  area  has  the  colour  of  the  final  orange  of 
the  firot  period,  the  upper  part  will  be  green  at  the  base  and  blue  at  the  top,  and  will  allow  of  the 
recognition  of  sharply  defined  colour-changes  of  distinctly  larger  radius. 

If  this  warming  be  continued  so  that  a  space  at  the  top  of  the  chamber  at  least  10  cm.  deep  is 
brought  to  a  temperature  of  about  50°  to  60^  C,  and  there  is  on  the  floor  of  the  diffraction  chamber 
(which  must  be  so  connected  with  the  air-filter  that  all  differences  of  pressure  brought  about  by  the 
warming  and  subsequent  cooling  may  be  equalised)  a  cold  and  wet  sponge  ;  then  a  cloud  forms  itself, 
which  first  originates  at  the  boundary  between  the  upper  warm  and  lower  cold  air,  and  rapidly  spreads 
from  below  downwards,  while  the  upper  part  of  the  glass  gradually  becomes  clear.  This  is  a  condition  of 
things  which  Alluabd  regularly  noticed  on  the  Puy  de  D6me,  in  the  winter  of  1879-80,  and  especially  in 
that  of  1881-2,  where,  for  example,  he  noticed  V'S  C.  at  Clermont  and  8°  C.  on  the  Puy  de  D6me.  If  the 
sun's  rays  be  allowed  to  enter  the  diffraction  chamber  parallel  to  this  boundary,  successive  cloud  layers 
will  be  seen  which  are  distinctly  marked  off,  one  from  the  other,  by  the  size  of  their  constituent  molecules, 
sharp  demarcations,  and  distinctness  of  colour.  The  colours  come  out  particularly  bright  if  a  reduction  of 
temperature  be  superinduced  upon  that  caused  by  diminution  of  pressure,  and  a  bluish  glowing  cloud 
appears  at  the  top  of  the  chambei;  to  vanish  again  in  a  few  seconds.     The  colour-changes  in  the  several 


ON  TH^:  LARGE  CORONA  ROUND  THE  SUN  AND  MOON       261 

layers  follow  the  same  order  from  above  downwards  (as  has  already  been  described),  in  the  central 
area  with  a  continued  fall  of  temperature.  These  colour-changes  seem  to  have  been  observed  by 
Alluard  on  the  Puy  de  D6me,  when  he  reports  (in  *  Comptes  Rendus/  vol.  xcviii.,  p.  162),  that  "  at 
sunrise  and  sunset  we  saw  all  the  colours  of  the  rainbow  successively  appear  on  the  horizon  in  every 
direction."  A  splendid  picture  of  cloud  structure  is  given  in  the  *  Leipzig  illustrirte  Zeitung  *  for  March 
the  8th,  from  a  sketch  by  Plumindon. 

If  the  colour-producing  cloud-layer  has  great  vertical  dimensions,  diffraction  rings  will  form  round 
the  sun  and  moon,  especially  when  at  low  altitude.  The  difiEraction  rings  round  the  sun  may  be 
observed,  even  when  only  faintly  developed,  by  pasting  a  black  disc  about  the  size  of  the  sun*s  image, 
on  the  back  of  a  blackened  glass,  and  looking  at  the  sun  with  one  eye  in  such  a  way  that  the  sun  shall 
be  covered  by  the  black  disc. 

PoLARiscopic  Observations  by  M.  Cornu.* 

The  corona  has  a  considerable  distui*bing  influence  on  atmospheric  polarisation,  especially  near  the 
neutral  points.  Since  the  appearance  of  the  corona,  the  relative  positions  of  the  three  neutral  points 
have  undergone  considerable  changes ;  moreover,  four  new  neutral  points  have  appeared  which  are 
situated  in  symmetrical  pairs  about  the  sun's  vertical,  nearly  at  the  altitude  of  the  solar  and  anti-solar 
centres.  The  two  neutral  points  right  and  left  of  the  sun  can  be  readily  seen  by  placing  a  piece  of 
red  glass  between  the  polariscope  and  the  eye  (the  face  and  the  other  eye  should  be  well  shaded) ;  they 
are  situated  outside  the  red  corona ;  a  green  glass  shows  the  neutral  points  less  distinctly,  and  a  cobalt 
blue  glass  brings  them  close  to  the  sun.  The  intensity  of  the  perturbation  decreases  then  with  the 
refrangibility  of  the  emitted  light;  the  analysis  of  the  polariscopic  phenomenon,  compared  with  that  of 
preceding  years,  shows  that  the  perturbation  corresponds  in  each  point  to  the  superposition  of  a  beam 
polarised  in  a  plane  perpendicular  to  a  plane  passing  through  the  sun. 

The  new  anti-solar  pair  of  neutral  points  are,  on  the  contrary,  difficult  of  observation ;  it  requires  a 
double  glass  {rouge  a  vitrail),  so  as  to  work  with  a  light  as  monochromatic  and  refrangible  as  possible. 
The  field  of  view  is  dark ;  nevertheless  the  coloured  bands  are  quito  distinct  when  the  sky  is  clear, 
but  they  can  be  seen  for  only  a  few  minutes  before  sunset.  There  is  a  similar  perturbation  in  the 
point  of  maximum  polarisation,  that  is,  at  90°  from  the  sun  in  the  vertical  line.  The  maximum  of 
polarised  light,  which  on  fine  days  might  usually  be  represented  by  0*75,  has  never  exceeded  0*48 ;  an 
accidental  diminution  in  the  amount  of  polarised  light  generally  corresponds  to  a  simple  increase  of 
haze ;  but  the  persistent  low  proportion  which  has  prevailed  under  all  meteorological  conditions,  taken 
in  connection  with  the  other  disturbances,  appears  to  indicate  the  existence  of  some  cause  which  acts 
like  haze  in  diffusing  neutral  light  and  diminishing  the  apparent  polarisation  of  blue  sky.  Photometric 
measurements  in  the  neighbourhood  of  the  sun  point  to  the  same  conclusion. 

Polarimetric  observations  made  with  a  red  or  a  cobalt-blue  glass  show  that  the  proportion  of  polarised 
light  is  less  for  the  red  than  for  the  blue  rays ;  here  again  the  degree  of  disturbance  diminishes  with  the 
refrangibility.  This  very  summary  account  will  not  warrant  any  rigorous  conclusions  as  to  the  cause 
of  the  phenomenon,  but  it  suffices  to  show  that  it  is  probably  related  to  the  eruption  of  Krakatoa. 


References  in  Section  I.  (e). 


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(*)  «Met.  Zeitschrift,'  vol.  i.  (1884),  p.  58. 
(»)  MSS.,  dated  December  8,  1884. 


*  '  Comptes  Rendns,*  vol.  xcix.  (1884),  p.  491,  et  seq. 
2  M 


262  REFERENCES  IN  SECTION  I.  (e). 

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(•)  •  Nature,'  vol.  xxix.  (1884),  p.  251. 

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(")  'Nature,'  vol.  xxix.  (1884),  p.  283. 

(»)  *  Met.  Zeitscbrift,'  vol.  i.  (1884),  p.  184. 

(")  « Met.  Zeitscbrift,'  vol.  i.  (1884),  p.  194. 

(")  'Nature,'  vol.  xxix.  (1884),  p.  403. 

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(")  'Nature,'  vol.  xxix.  (1884),  p.  260. 

(»)  '  Nature,'  vol.  xxix.  (1883),  p.  130. 

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(«)  '  Nature,'  vol.  xxix.  (1884),  p.  309. 

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(«)  'Nature,'  vol.  xxxi.  (1885),  p.  548. 

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